Anansi

An MCP server that speaks GraphQL. Named for the spider who owns all stories: instead of exposing one tool per endpoint, Anansi spins your backend into a single typed web. The agent reads the schema, then composes exactly the query it needs — nested relations in one call, only the fields it wants.

Ships with a mock blog dataset (users → posts → comments) so you can try it the moment you clone it.

Why

Concern	Tool-per-endpoint MCP server	Anansi
Tool count	Grows with the API (tool explosion)	4 fixed tools
Over-fetching	Full payloads → wasted tokens	Agent selects only needed fields
Related data	One round trip per relation	Nested selections, single call
Discoverability	Prose tool descriptions	Typed schema (SDL) with doc strings
Self-correction	Errors only after execution	Pre-flight graphql_validate + structured GraphQL errors

Quickstart

No clone needed (any MCP client)

With uv installed, add this to your MCP client config (Claude Desktop, VS Code, etc.):

{
  "mcpServers": {
    "anansi": {
      "command": "uvx",
      "args": ["anansi-mcp"],
      "env": { "ANANSI_ALLOW_MUTATIONS": "1" }
    }
  }
}

From source

Requires Python 3.10+.

git clone https://github.com/NarglesCS/anansi.git
cd anansi
python -m venv .venv

# Windows
.venv\Scripts\python.exe -m pip install -e ".[dev]"
.venv\Scripts\python.exe -m pytest -q     # verify: 12 tests

# macOS / Linux
.venv/bin/python -m pip install -e ".[dev]"
.venv/bin/python -m pytest -q

Interacting with it

Option 1 — MCP Inspector (fastest way to poke at the mock data)

npx @modelcontextprotocol/inspector .venv/Scripts/python.exe -m anansi.server

Opens a browser UI where you can list the tools, read the graphql://schema resource, and run queries by hand.

Option 2 — VS Code agent mode

.vscode/mcp.json is preconfigured. Open the repo in VS Code, start the anansi server from the MCP view, then ask Copilot agent mode things like "Who commented on Grace Hopper's posts?" and watch it discover the schema and compose queries.

Option 3 — Any MCP client (Claude Desktop, etc.)

{
  "mcpServers": {
    "anansi": {
      "command": "/absolute/path/to/anansi/.venv/bin/python",
      "args": ["-m", "anansi.server"],
      "env": { "ANANSI_ALLOW_MUTATIONS": "1" }
    }
  }
}

(On Windows the command is ...\anansi\.venv\Scripts\python.exe.)

What the server exposes

Kind	Name	Purpose
Resource	graphql://schema	The SDL, loadable as context up front
Tool	graphql_schema()	Same SDL for clients that prefer tools over resources
Tool	graphql_validate(query)	Parse + validate + measure depth without executing
Tool	graphql_query(query, variables?)	Read-only execution; mutations rejected
Tool	graphql_mutate(mutation, variables?)	Writes, only when ANANSI_ALLOW_MUTATIONS=1

Example: query the mock data

query($role: Role) {
  users(role: $role) {
    name
    posts(limit: 2) {
      title
      comments { author { name } text }
    }
  }
}

with variables {"role": "ADMIN"} returns, in one round trip:

{"data": {"users": [{"name": "Ada Lovelace", "posts": [{"title": "...", "comments": [...]}]}]}}

Example: write to the mock data

mutation($input: CreatePostInput!) {
  createPost(input: $input) { id published }
}

with {"input": {"authorId": "u3", "title": "Hello", "body": "..."}}. The store is in-memory — restart the server and you're back to the seed data.

Configuration

Env var	Default	Effect
ANANSI_ALLOW_MUTATIONS	off	Set to 1 to enable graphql_mutate
ANANSI_MAX_DEPTH	10	Max query nesting depth (fragment-cycle safe)
ANANSI_MAX_COMPLEXITY	100	Max total fields selected per request (breadth guard)
ANANSI_MAX_RESULT_BYTES	262144	Max serialized result size; 0 disables

Other rails: graphql_query hard-rejects mutations, subscriptions are always rejected, and all errors come back as standard GraphQL {message, locations, path} shapes that models know how to read and repair. Guard failures include a remediation hint so agents can self-correct. Repeated queries skip re-parsing/re-validation via an internal cache (execution is never cached).

How it's built

flowchart LR
    Agent["AI agent (MCP client)"] -- "MCP stdio" --> Tools

    subgraph Anansi["Anansi server"]
        direction TB
        Tools["Tools: graphql_query / graphql_validate / graphql_mutate / graphql_schema"]
        Schema["Resource: graphql://schema (SDL)"]
        Engine["Engine: parse → gate ops → validate → depth-check → execute"]
        Resolvers["Resolvers"]
    end

    Tools --> Engine --> Resolvers --> Store[("In-memory mock store<br/>(swap for DB / REST fan-out / services)")]
    Agent -. "reads schema" .-> Schema

Each layer is independently swappable:

• src/anansi/data.py — in-memory mock dataset. Replace with any real backend.
• src/anansi/schema.py — SDL with doc strings (they travel to the model) + resolver wiring.
• src/anansi/engine.py — execution pipeline with safety rails; no MCP dependency.
• src/anansi/server.py — thin MCP wiring: tools, resource, instructions.

Roadmap ideas

• Swap data.py for a real datasource (SQL, REST fan-out, microservices) — the classic GraphQL gateway pattern, now agent-facing.
• Per-field auth, query cost analysis, timeouts, result-size caps.
• Persisted-query allowlists for high-trust deployments.
• GraphQL subscriptions mapped onto MCP notifications.

License

MIT

Contributions and issues welcome.