Fbdl

MCP server for Meta's FBDL (Facebook Developer Language). Lets AI agents generate, validate, and explore FBDL scripts used in Meta's bug bounty program (MMBRC).

No auth required -- FBDL is a text format. This server runs locally and never talks to Meta's infrastructure.

• fbdl-mcp
  • What it does
  • Install
  • Setup with Claude Code
  • Setup with OpenAI Codex / agents
    • AGENTS.md snippet
  • Example workflow
  • FBDL quick reference
    • Setup block
    • Action lines
    • Rules
  • Development
  • Project structure

What it does

• validate_fbdl -- Parse and validate FBDL scripts. Catches unknown entities/actions, missing required params, invalid enum values, bad syntax.
• list_entities -- Browse all setup entity types (User, Page, Group, Album, Friendship, Business, App, Event) with their params and examples.
• list_actions -- Browse all 70+ FBDL actions with signatures, params, and examples. Filter by name or category.
• explain_fbdl -- Turn an FBDL script into a plain-English step-by-step explanation.
• generate_fbdl (prompt) -- Prompt template that gives the calling LLM the full FBDL grammar so it can generate valid scripts from natural language.

Claude Code skills (no MCP server needed)

The repo includes standalone Claude Code skills that work without the MCP server. Copy the .claude/skills/ directory into any project:

cp -r /path/to/fbdl-mcp/.claude/skills/ your-project/.claude/skills/

Available skills:

• /generate-fbdl -- Generate FBDL scripts from natural language. Embeds the full grammar reference so Claude can produce valid scripts directly.
• /validate-fbdl -- Validate FBDL scripts against the grammar. Includes a complete checklist of structure, entity, action, and reference checks.

These skills embed the entire FBDL spec as prompt context -- no server, no dependencies, no build step.

Install

git clone <repo-url> && cd fbdl-mcp
npm install
npm run build

Verify everything works:

npm run check   # typecheck + lint + format + tests

Setup with Claude Code

Add to your Claude Code MCP config (~/.claude/settings.json or project .claude/settings.json):

{
  "mcpServers": {
    "fbdl": {
      "command": "node",
      "args": ["/absolute/path/to/fbdl-mcp/dist/server.js"]
    }
  }
}

Then in Claude Code you can say things like:

"Generate an FBDL script where two users are friends, one owns a page, the other posts a photo and gets blocked"

"Validate this FBDL script: [setup] User UserOne Page PageOne with {owner: UserOne}"

"What FBDL actions are available for groups?"

Setup with OpenAI Codex / agents

For Codex or any MCP-compatible agent, point it at the server binary:

node /absolute/path/to/fbdl-mcp/dist/server.js

The server communicates over stdio using the MCP protocol. It exposes:

• 4 tools: validate_fbdl, list_entities, list_actions, explain_fbdl
• 1 resource: fbdl://reference (full language spec as markdown)
• 1 prompt: generate_fbdl (NL-to-FBDL prompt template)

AGENTS.md snippet

If your agent framework uses AGENTS.md for tool discovery, add:

## FBDL MCP Server

Tools for working with Meta's FBDL (Facebook Developer Language) scripts:

- Use `validate_fbdl` after generating a script to check it for errors
- Use `list_entities` and `list_actions` to discover available FBDL constructs
- Use `explain_fbdl` to understand what an existing script does
- Use the `generate_fbdl` prompt to produce scripts from natural language

The server runs on stdio. Start with: `node /path/to/fbdl-mcp/dist/server.js`

Example workflow

1. Agent receives: "Create a test scenario where a page admin blocks a group member"

2. Agent calls list_entities to check what setup is needed

3. Agent calls list_actions with category: "block" to find the right action

4. Agent uses the generate_fbdl prompt to produce:

[setup] User OwnerOne User MemberOne Page PageOne with {owner: OwnerOne} Group GroupOne with {owner: OwnerOne, privacy: private, members: [MemberOne]}
OwnerOne as PageOne block MemberOne

5. Agent calls validate_fbdl to verify the script is correct

6. Researcher pastes the script into Meta's MMBRC platform

FBDL quick reference

Setup block

[setup] Type Label [with {key: value, ...}] [Type Label ...]

Entity types: User, Page, Group, Album, Friendship, Business, App, Event

Action lines

Subject [as VoiceSwitcher] action_name Label [with {key: value, ...}]

Voice switcher (as) lets a user act as a page they own.

Rules

• All entities must be created in setup before use in actions
• The setup block is a single line starting with [setup]
• Each action goes on its own line
• Labels are PascalCase and must be unique

Development

npm run build         # compile TypeScript
npm run test          # run tests
npm run lint          # eslint with strict TypeScript rules
npm run format        # prettier
npm run check         # all of the above

Project structure

src/
  schema.ts           # FBDL language spec as typed data (entities + actions)
  validator.ts        # FBDL script parser and validator
  server.ts           # MCP server (tools, resources, prompts)
  __tests__/
    schema.test.ts    # Schema integrity tests
    validator.test.ts # Validator correctness tests
    server.test.ts    # MCP tool integration tests