Curl Curl Cool

CI

An MCP server that gives Claude a full HTTP client — make requests, compare environments, infer TypeScript types from live responses, and work directly with your existing Postman collections and environments.

Built with the Model Context Protocol TypeScript SDK, native fetch (no Axios), and a provider pattern that keeps every tool unit-testable without network calls.

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Tools

Tool	Description
http_request	Make an HTTP request and return status, headers, and body. JSON responses are pretty-printed. Supports auth, custom headers, body, and {{variable}} substitution.
diff_environments	Fire the same request against multiple environments in parallel and show what differs in status codes and response bodies — field by field.
generate_types	Infer TypeScript interface declarations from a JSON string. Nested objects become named interfaces. Chain after http_request to generate types from a live API response.
load_collection	Parse an OpenAPI 3.0 spec or Postman Collection v2.1 and list all endpoints. Shows pre-defined headers, body, and collection variables.
load_postman_environment	Load a Postman environment file and list its variables, masking secrets. Use the values to resolve {{placeholders}} in collection URLs.
get_response_history	List recent requests made in this session with status and timing. Resets when the server restarts.

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Installation

Via npm (recommended)

npm install -g curl-curl-cool-mcp

Or use it without installing — npx will fetch and run it on demand (see Claude config below).

From source

git clone https://github.com/dicoy/curl-curl-cool-mcp.git
cd curl-curl-cool-mcp
npm install
npm run build

Add to Claude Desktop

Add to ~/Library/Application Support/Claude/claude_desktop_config.json on macOS:

{
  "mcpServers": {
    "httpclient": {
      "command": "npx",
      "args": ["-y", "curl-curl-cool-mcp"]
    }
  }
}

Add to Claude Code

claude mcp add httpclient -- npx -y curl-curl-cool-mcp

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Works with Postman

This is where it gets interesting. If you configure this server alongside Postman's official MCP server, Claude becomes the orchestrator between them — browsing your Postman workspace with one server and executing requests with this one.

Why this matters

Postman's MCP server gives Claude access to your workspace: it can list collections, read request definitions, and fetch environment values directly from the Postman API. But it doesn't execute requests.

This server is the execution layer. Together, they let Claude go from "find the endpoint" to "run it, diff it across environments, and generate TypeScript types for the response" in a single conversation — without you copy-pasting a single URL.

Setup

Add both servers to your Claude config (~/Library/Application Support/Claude/claude_desktop_config.json on macOS):

{
  "mcpServers": {
    "httpclient": {
      "command": "npx",
      "args": ["-y", "curl-curl-cool-mcp"]
    },
    "postman": {
      "command": "npx",
      "args": ["-y", "@postman/postman-mcp-server"],
      "env": {
        "POSTMAN_API_KEY": "your-api-key-here"
      }
    }
  }
}

Get your Postman API key from Postman → Account Settings → API Keys.
See Postman's MCP server docs for the full setup guide.

Example workflows

Once both servers are configured, you can give Claude prompts like these:

Explore and execute:

"Find the Create Order endpoint in my Payments collection on Postman, load the staging environment, and make a test request."

Claude calls Postman MCP to find the endpoint definition, then calls load_postman_environment and http_request here to execute it.

Cross-environment diff:

"Run the GET /users endpoint from my API collection against dev and prod and tell me what's different."

Claude resolves the base URLs from two environment files and calls diff_environments, which fires both requests in parallel and shows field-level diffs.

Type generation from live data:

"Hit the /products endpoint on staging and generate TypeScript types for the response."

Claude chains http_request → generate_types — no copy-pasting JSON.

Variable substitution

Postman collections use {{variable}} placeholders for environment-specific values. Both http_request and diff_environments resolve these natively, so Claude can pass data from Postman MCP straight through without manual substitution.

Single request with variables:

http_request({
  url: "{{base_url}}/api/{{version}}/users/{{user_id}}",
  variables: {
    base_url: "https://api.example.com",
    version:  "v2",
    user_id:  "42"
  }
})

Multi-environment diff with per-env variable maps:

diff_environments({
  path: "{{base_url}}/api/users",
  environments: {
    dev:  { base_url: "https://api-dev.example.com" },
    prod: { base_url: "https://api.example.com"     }
  }
})

Unresolved placeholders are left intact so Claude can see what's missing rather than silently sending a broken URL.

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Authentication

http_request and diff_environments both support three auth mechanisms via the auth parameter:

Type	Parameters	Header produced
bearer	token	Authorization: Bearer <token>
basic	username, password	Authorization: Basic <base64>
api-key	header (default: X-API-Key), value	<header>: <value>

Explicit headers always take precedence over auth, so you can override if needed.

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Architecture

src/
├── providers/           # Interfaces + implementations (injectable for tests)
│   ├── http.ts          # IHttpProvider / NodeFetchProvider (native fetch, AbortController)
│   ├── history.ts       # IHistoryProvider / InMemoryHistoryProvider (max 20 entries)
│   ├── collection.ts    # ICollectionProvider / FsCollectionProvider (OpenAPI + Postman)
│   └── postman-environment.ts  # IPostmanEnvironmentProvider / FsPostmanEnvironmentProvider
├── tools/               # One directory per tool: schema.ts + handler.ts + handler.test.ts
├── utils/
│   ├── auth.ts          # resolveAuthHeaders — shared by http_request + diff_environments
│   └── variables.ts     # substituteVariables — {{placeholder}} resolution
└── registry/
    └── tool-registry.ts # Wires providers into MCP tool registrations

Each tool handler is a pure function (input, ...providers) => string. Providers are injected, so tests mock the interface rather than the network or filesystem. 44 unit tests, zero network calls.

Tech: TypeScript 5 (strict + exactOptionalPropertyTypes), MCP SDK, Zod, Biome, Vitest, tsup.