Agda Server

npm version CI License: MIT Node >=24

agda-mcp-server is a stateful Model Context Protocol server for interactive Agda proof development.

It keeps a long-running Agda process alive in --interaction-json mode so MCP clients can use Agda the way a human does in an editor: load a file, inspect goals, split on variables, refine holes, infer types, normalize expressions, search the local environment, and iterate on proofs without restarting Agda for every request.

What this server provides

• Persistent interactive Agda sessions.
• Goal-aware proof actions over MCP.
• Stateless batch type-checking when you only want a quick validation pass.
• Navigation and scope-inspection helpers for large Agda codebases.
• Literate Agda support — extract code blocks from all seven literate formats.
• Structured semantic outputs for every tool, alongside human-readable text.
• Agent-native session introspection (agda_session_snapshot, agda_goal_catalog, agda_tool_recommend).
• Bug-report and issue-update bundle generation with stable fingerprints.
• A small extension system for project-specific or domain-specific tools.

How it works

The server launches Agda in --interaction-json mode and communicates through Agda's IOTCM protocol over standard input and output.

In practice, the workflow is:

1. Load an Agda file with agda_load.
2. Agda assigns interaction point IDs to all open goals.
3. Use those goal IDs with proof-oriented tools such as agda_goal_type, agda_case_split, agda_refine, or agda_give.
4. Reload the file after applying source edits so Agda can refresh its goals.

This statefulness is the main difference between agda_load and the stateless agda_typecheck command.

Requirements

Before using the server, make sure you have:

• Node.js >= 24
• An Agda installation available as agda on your PATH, or
• A repo-local pinned runner at tooling/scripts/run-pinned-agda.sh

If both are available, the pinned runner is preferred.

Installation

From source

npm install
npm run build

This produces the distributable server in dist/.

Local CLI entry point

After building, the executable entry point is:

node dist/index.js

The published package also exposes the agda-mcp-server binary through the bin field in package.json.

Use --help or --version to inspect the installed binary without starting the MCP server:

agda-mcp-server --version   # prints the server version
agda-mcp-server --help      # prints usage and all environment variables

Quick start

Start the server on stdio with a project root:

AGDA_MCP_ROOT=/path/to/agda/project node dist/index.js

If AGDA_MCP_ROOT is omitted, the current working directory is used.

Examples

Example: load a file and inspect goals

1. agda_load file="Nat/Properties.agda"
  → reports load status and goal IDs

2. agda_session_status
  → shows the loaded file and active goals

3. agda_goal_type goalId=0
  → returns the local context and expected type for `?0`

Example: refine a proof hole

1. agda_goal_type goalId=0
  → inspect the goal before editing

2. agda_refine goalId=0 expr="suc"
  → apply a constructor or function

3. agda_metas
  → inspect any new subgoals created by the refinement

Example: check an expression before committing to it

1. agda_elaborate goalId=0 expr="map f xs"
  → see Agda's elaborated form

2. agda_infer goalId=0 expr="map f xs"
  → confirm the inferred type

3. agda_give goalId=0 expr="map f xs"
  → fill the goal once the expression looks correct

Example: stateless validation in CI or editor automation

agda_typecheck file="MyModule.agda"

Use this when you want errors and warnings without creating a persistent session.

Semantic outputs

Every tool returns:

• Human-readable text for existing MCP clients (in content[].text).
• Structured content with stable envelope fields (tool, ok, classification, summary, data, diagnostics, provenance, elapsedMs).

Every tool's data carries at least the rendered text plus a tool-specific structured payload — e.g. solutions / rawSolutions / written for agda_solve_*, parsed clauses for agda_case_split, goalType and context arrays for goal queries, success and output for backends, display-state snapshots for the toggle/show family, and so on. Agents should prefer the structured fields over scraping the markdown body.

Core session tools (agda_load, agda_load_no_metas, agda_typecheck) expose completeness fields — goalCount, invisibleGoalCount, hasHoles, isComplete, and a classification of ok-complete / ok-with-holes / type-error — derived from a merged source-hole + protocol-counts signal so explicit hole markers ({!!} / ?) inside abstract blocks cannot trick the load into a false ok-complete.

MCP client configuration

Claude Code

Add a server entry similar to this in your Claude Code settings:

{
  "mcpServers": {
    "agda": {
      "command": "node",
      "args": ["mcp/agda-mcp-server/dist/index.js"],
      "env": {
        "AGDA_MCP_ROOT": "."
      }
    }
  }
}

Other MCP clients

Any MCP client that can spawn a stdio server can run this package. Use the same pattern:

• command: node
• args: path to dist/index.js
• environment: set AGDA_MCP_ROOT to the Agda project root

Session model

This server is intentionally stateful.

• One shared Agda session is kept alive.
• The session tracks the currently loaded file.
• Goal IDs are meaningful only for the currently loaded file and current Agda state.
• If the file changes on disk, reload it with agda_load before continuing.

If you only want a quick compile check and do not need goals, use agda_typecheck instead of creating a session.

Write-back for proof actions

The proof-action tools (agda_give, agda_refine, agda_refine_exact, agda_intro, agda_auto, agda_case_split, agda_solve_one, agda_solve_all) persist their result to the source file by default and auto-reload, so the session and disk stay in sync without a separate edit step. Pass writeToFile: false on any of those calls for session-only behavior (old default).

agda_apply_edit(file, oldText, newText, occurrence?) is a sibling primitive for non-goal edits — adding imports, renaming symbols, fixing typos. It substitutes oldText with newText in the named file and reloads. oldText must match exactly once unless occurrence (1-based) is provided.

Both paths share the same safety guarantees:

• Agda source files only. agda_apply_edit refuses anything outside the .agda / .lagda[.md/.rst/.tex/.org/.typ] allowlist — it cannot be used to modify .git/config, package.json, shell scripts, or other non-Agda files inside the project root.
• Path containment. All edits resolve the target path through realpath and verify it stays inside the project root; a symlink that physically points outside the root is refused.
• Symlink race defense. Source reads use O_NOFOLLOW; if a symlink is planted at the canonical path after path resolution, the read fails with ELOOP instead of silently following it.
• File size cap. The edit pipeline refuses to read or write any Agda source file larger than 512 KiB (524288 bytes). This protects memory, scanner cost, and blast radius — it is a deliberate soft cap, not a protocol limit. If you have a legitimate Agda source file that trips this, treat it as a sign that the file should be split rather than as a bug to work around.
• Atomic writes. Edits go through a temp-file-rename so readers never observe a partially-written state. The temp filename mixes pid and randomUUID() and is created with O_EXCL so it cannot be pre-planted by a concurrent process.
• Staleness guard. If the loaded file has been modified on disk since the last agda_load, the edit is refused and the session is reloaded to match disk — writes never clobber external changes.

Tool reference

Protocol coverage

This repository now tracks full command-inventory parity with Agda's interactive IOTCM command constructors listed in Agda.Interaction.Base (verification date: 2026-03-24).

• The current protocol inventory lives in src/protocol/command-registry.ts.
• The protocol parity matrix lives in src/protocol/parity-matrix.ts.
• The inventory and parity tests enforce that every tracked upstream command has a parity row, but semantic parity is tracked separately from mere command mapping.
• Architecture still keeps a clean separation between transport, protocol decoding, and MCP presentation layers.

Use agda_protocol_parity for the current matrix, including known gaps.

At the current milestone, the server now exposes:

• agda_goal_type_context_infer for goal, context, and inferred-type queries
• agda_goal_type_context_check for goal, context, and checked-term queries
• agda_goal for exact goal-only display
• agda_context for exact context-only display
• agda_refine_exact for exact Cmd_refine
• agda_intro for exact Cmd_intro
• agda_solve_one for exact Cmd_solveOne
• agda_load_no_metas for strict loading without unresolved goals
• agda_abort and agda_exit for process control
• agda_show_version for the running Agda process version
• agda_load_highlighting_info, agda_token_highlighting, and agda_highlight for highlighting control
• agda_show_implicit_args / agda_toggle_implicit_args and agda_show_irrelevant_args / agda_toggle_irrelevant_args for display toggles
• agda_compile, agda_backend_top, and agda_backend_hole for backend interaction commands
• agda_tools_catalog for manifest-derived tool and schema introspection
• agda_session_snapshot for one-call agent session introspection with suggested actions
• agda_goal_catalog for one-call full proof-state inspection across all goals
• agda_tool_recommend for priority-ordered next-tool recommendations based on proof state
• agda_bug_report_bundle and agda_bug_report_update_bundle for structured bug intake

Session management

Tool	Description
agda_load	Load and type-check a file, establish the active interactive session, and return current goal IDs
agda_load_no_metas	Load and type-check a file, failing if any unsolved metavariables remain
agda_session_status	Show the currently loaded file and available goal IDs
agda_show_version	Show the version string reported by the running Agda process
agda_abort	Send Agda's Cmd_abort to the running process
agda_exit	Send Agda's Cmd_exit to the running process
agda_typecheck	Run a stateless batch type-check without creating or updating the interactive session
agda_apply_edit	Apply a targeted text substitution to an Agda source file and reload (imports, renames, typos; Agda files only)
agda_tools_catalog	Return the manifest-derived catalog of tools, categories, and schema field names

Display and highlighting

Tool	Description
agda_load_highlighting_info	Load highlighting metadata for a file
agda_token_highlighting	Keep or remove token highlighting output for a file
agda_highlight	Highlight an expression in a goal context
agda_show_implicit_args	Set implicit-argument visibility
agda_toggle_implicit_args	Toggle implicit-argument visibility
agda_show_irrelevant_args	Set irrelevant-argument visibility
agda_toggle_irrelevant_args	Toggle irrelevant-argument visibility

Backend commands

Tool	Description
agda_compile	Compile a module through Agda using a selected backend (Cmd_compile)
agda_backend_top	Send backend-specific top-level payload (Cmd_backend_top)
agda_backend_hole	Send backend-specific goal-hole payload (Cmd_backend_hole)

Reporting and agent introspection

Tool	Description
agda_session_snapshot	Return a structured snapshot of session state: phase, goal counts, completeness, staleness, and prioritised suggested next actions
agda_tool_recommend	Suggest likely next MCP tool calls ordered by priority, with rationale and pre-filled arguments
agda_bug_report_bundle	Generate a structured bundle for a new bug report or regression
agda_bug_report_update_bundle	Generate a structured bundle for updating an existing bug report with new data

Goal inspection and proof interaction

These tools require a file to be loaded first via agda_load.

Tool	Description
agda_goal_catalog	Return a structured catalog of all open goals: types, contexts, splittable variables, and per-goal suggestions
agda_goal_type	Show the goal type and local context for one interaction point
agda_goal	Show only the goal type for one interaction point
agda_context	Show only the local context for one interaction point
agda_metas	List unsolved goals in the loaded file
agda_case_split	Case-split on a variable in a goal and return the generated clauses
agda_give	Fill a goal with a proposed expression
agda_refine	Refine a goal by applying a function or constructor
agda_refine_exact	Refine a goal using Agda's exact Cmd_refine command
agda_intro	Introduce a lambda or constructor using Agda's exact Cmd_intro command
agda_auto	Attempt proof search for a single goal
agda_auto_all	Attempt proof search across all goals
agda_solve_all	Solve goals that have unique solutions
agda_solve_one	Solve one goal if Agda already knows it has a unique solution
agda_compute	Normalize an expression, either in goal context or at top level
agda_infer	Infer the type of an expression, either in goal context or at top level
agda_constraints	Show Agda's current constraint set
agda_elaborate	Elaborate an expression in a goal context
agda_helper_function	Generate a helper function type from a goal-local expression
agda_goal_type_context_infer	Show a goal's context and type together with the inferred type of an expression
agda_goal_type_context_check	Show a goal's context and type together with the checked elaborated form of an expression

Navigation and environment inspection

Tool	Description
agda_read_module	Read a module from disk with line numbers; pass codeOnly: true to extract just Agda blocks from literate files
agda_list_modules	List Agda modules in a directory tier; paginated (offset, limit, pattern) with total count in every response
agda_impact	List files that transitively import a given file — direct and transitive dependents and dependencies
agda_cache_info	Show the .agdai interface cache paths for the loaded file
agda_check_postulates	Check a file for postulate declarations
agda_search_definitions	Search source files for matching identifiers or text
agda_why_in_scope	Explain why a name is in scope, either at top level or in a goal
agda_show_module	Show what a module exports
agda_search_about	Search the loaded environment for names whose types mention the query

Typical interactive workflow

1. agda_load file="MyModule.agda"
     → Status: OK, 3 unsolved goals (?0, ?1, ?2)

2. agda_goal_type goalId=0
     → Context: (x : Nat), (p : x ≡ zero)
     → Goal: x + zero ≡ x

3. agda_auto goalId=0
     → No automatic solution found.

4. agda_elaborate goalId=0 expr="+-identityʳ x"
     → Elaborated: +-identityʳ x : x + zero ≡ x

5. agda_give goalId=0 expr="+-identityʳ x"
     → Goal solved.

6. Apply edits to the source file if needed.

7. agda_load file="MyModule.agda"
     → Reload to refresh remaining goals.

Stateless vs stateful operations

Use agda_typecheck when you want:

• a quick yes or no answer about whether a file checks,
• error and warning output only,
• no interactive goal information,
• no persistent Agda session.

Use agda_load when you want:

• stable goal IDs,
• interactive commands against holes,
• proof search, refinement, elaboration, and local type information,
• a persistent Agda subprocess.

Environment variables

Variable	Default	Description
AGDA_MCP_ROOT	cwd	Root directory used to resolve Agda files and relative extension paths
AGDA_MCP_EXTENSION_MODULES	unset	Colon-separated list of extension module paths or package specifiers

Extension modules

The core server is intentionally generic and supports external extension modules.

For complete setup instructions and multiple extension examples, see:

• docs/extensions.md
• examples/extensions/README.md

Development

Scripts

Script	Purpose
npm run build	Compile TypeScript into dist/
npm run dev	Run the TypeScript entry point directly with tsx
npm test	Build first, then run the Node test suite
npm run test:examples	Run tests focused on extension examples and extension docs links
npm run test:integration	Run the Agda-backed integration test scaffold
npm run verify	Run tests and verify package contents with npm pack --dry-run

Local development flow

npm install
npm run build
npm test
npm run verify

Tests

The test suite currently focuses on lightweight, deterministic behavior such as:

• response parsing,
• Agda command string escaping,
• Agda binary discovery,
• session cleanup behavior.

The tests intentionally avoid depending on a live Agda installation so they can run reliably in normal CI environments.

An integration scaffold is also available for environments where Agda is installed:

RUN_AGDA_INTEGRATION=1 npm run test:integration

Backend integration commands can be exercised with:

RUN_AGDA_BACKEND_INTEGRATION=1 AGDA_BACKEND_EXPR=GHC npm run test:integration

AGDA_BACKEND_EXPR accepts backend constructor expressions such as GHC, GHCNoMain, LaTeX, QuickLaTeX, or OtherBackend "Name".

Publishing

The package is configured for public npm publishing.

Before publishing:

1. Update the version in package.json.
2. Run npm run verify.
3. Publish with npm using your normal release process.

The prepublishOnly script runs verification automatically before publish.

Only the following files are published:

• dist/
• README.md
• LICENSE

Continuous integration

This repository includes a GitHub Actions workflow at .github/workflows/ci.yml that:

• installs dependencies with npm ci,
• runs on pushes and pull requests,
• verifies the package on Node.js 24.

Community and maintenance files

This repository also includes:

• CONTRIBUTING.md for contributor setup and workflow guidance
• SECURITY.md for vulnerability reporting guidance
• CHANGELOG.md for release history
• .github/ISSUE_TEMPLATE/config.yml and issue forms for structured reports
• .github/pull_request_template.md for consistent pull requests
• .nvmrc and the packageManager field in package.json for local toolchain alignment

Architecture overview

src/
  index.ts
    Bootstraps the MCP server, registers core tools, and loads extensions.

  agda-process.ts
    Public barrel for the Agda integration layer.

  agda/
    session.ts
      Owns the Agda subprocess, transport, buffering, and session state.
    batch.ts
      Stateless batch type-checking.
    goal-operations.ts
      Goal-centric interactive commands.
    expression-operations.ts
      Expression normalization and type inference.
    advanced-queries.ts
      Constraints, scope, elaboration, module inspection, and search.
    display-operations.ts
      Highlighting and display-toggle command delegates.
    backend-operations.ts
      Compile and backend payload command delegates.
    backend-expression.ts
      Backend expression validation and normalization.
    response-parsing.ts
      Helpers for extracting user-facing messages from Agda responses.
    types.ts
      Shared types for the Agda integration layer.

  protocol/
    command-registry.ts
      Upstream command inventory and parity metadata.
    responses/
      goal-display.ts
      proof-actions.ts
      process-controls.ts
      backend.ts
        Focused response decoders per command family.

  tools/
    session.ts
      MCP tool registration for loading and status operations.
    proof.ts
      MCP tool registration for goal-oriented proof actions.
    navigation.ts
      MCP tool registration for source and environment navigation.
    display.ts
      MCP tool registration for highlighting and display toggles.
    backend.ts
      MCP tool registration for compile and backend payload commands.

  session/
    session-state.ts
      High-level session phase derivation used to keep process lifecycle concerns explicit.

Protocol notes

The server communicates with Agda using the IOTCM protocol over --interaction-json mode.

At a high level:

• commands are written to Agda on stdin as IOTCM strings,
• Agda emits newline-delimited JSON responses on stdout,
• stderr output is captured for diagnostics,
• session completion is inferred from status and running-info messages.

Troubleshooting

agda cannot be found

Make sure either:

• agda is installed and on your PATH, or
• tooling/scripts/run-pinned-agda.sh exists in the repo root.

Goal IDs stop working

Goal IDs are tied to the current loaded file and the current Agda state. If the source changed or you applied a case split, reload the file with agda_load.

Top-level commands fail with "No file loaded"

Most interactive commands require an active loaded file because they need the Agda session context. Start with agda_load.

Proof search or elaboration returns unexpected output

Agda response formatting varies across commands. When in doubt, inspect the goal again with agda_goal_type and retry with a simpler expression.

License

This project is licensed under the MIT License. External extension modules may use different licenses.