universal-connector-mcp 0.1.1

A security-first, local-first MCP server that connects any API (OpenAPI/GraphQL/gRPC/SOAP) to AI agents through a single normalized operation model.

Universal API Connector MCP

Any API. One MCP server.

Stop installing a new MCP server for every service: point this one at any OpenAPI/Swagger, GraphQL,
gRPC or SOAP spec - or pick one from the built-in catalog of 2500+ public APIs - and your AI agent
can call it. Securely, in fewer steps, with fewer tokens.

Installation · Meta-tools · API catalog · Examples · Configuration · Security

Why another one?

Most "universal API" MCP servers only speak REST/OpenAPI. This project is built around three differentiators:

1. Truly universal - a normalized Operation model with pluggable spec adapters (OpenAPI, GraphQL, gRPC, SOAP). Tools and executors never care which protocol produced an operation.
2. Security-first / local-first - a direct response to supply-chain attacks like the AgentBaiting / FakeGit campaign. Outbound requests are restricted to an allowlist, secrets never touch logs, responses are size-capped, and every call is audit-logged. No arbitrary code execution, no binary downloads, no telemetry.
3. Built for context efficiency - field-level response filtering, chained and parallel execution, and response caching mean whole workflows fit in one tool call and responses stay small.

How it works

The agent explores APIs like a filesystem instead of loading hundreds of tools at once (which would blow up the context window on large APIs like Stripe). It searches for operations, inspects the ones it needs, then executes them.

Architecture (click to expand)

flowchart TD
    Agent["AI Agent"] -->|"MCP stdio"| Server["FastMCP Server"]
    Server --> Tools["Meta-tools"]
    Tools --> Registry["Operation Registry (normalized)"]
    Adapters["Spec Adapters"] --> Registry
    Tools --> Guard["Security Guard"]
    Guard --> Executor["Protocol Executors"]
    Executor --> Auth["Auth Manager"]
    Executor --> UpstreamAPI["Upstream API"]

Meta-tools

Tool	Purpose
search_catalog	Find ready-to-load public APIs (curated list + APIs.guru directory, 2500+ specs)
load_api	Register an API from a spec URL/file (protocol auto-detected)
list_apis	List loaded APIs
search_operations	Fuzzy-search operations across loaded APIs
get_operation	Full parameter/response schema for one operation
execute	Call an operation (auth + security guard applied); extract returns only the fields you ask for
execute_chained	Run a sequence of operations in one call, piping results between steps; nested lists run in parallel
unload_api	Remove a loaded API
audit_log	Recent outbound calls (method, host, path, status)

Why fewer steps (and fewer tokens)

Where a per-API MCP server needs one tool round-trip per call - each returning a full JSON payload into the agent's context - this server collapses whole workflows:

• extract - execute(..., extract=["items.*.name", "total_count"]) returns just those fields instead of a multi-kilobyte response. * fans out over arrays.
• Chaining - execute_chained pipes step results into later params via ${save_as.path} references: one tool call instead of N.
• Parallel groups - a nested list of steps runs concurrently, so "query three APIs and combine" is still one call:

execute_chained(steps=[
  [
    {"operation_id": "github.repos_get", "params": {"owner": "o", "repo": "r"},
     "save_as": "gh", "extract": ["stargazers_count"]},
    {"operation_id": "open_meteo.get_v1_forecast", "params": {"latitude": 52.5, "longitude": 13.4},
     "save_as": "weather", "extract": ["current_weather.temperature"]}
  ],
  {"operation_id": "github.issues_list_for_repo",
   "params": {"owner": "o", "repo": "r"}, "extract": ["*.title"]}
])

• Response cache - successful GET/query results are cached for UCMCP_CACHE_TTL seconds (default 60), so repeated lookups are instant and free; pass fresh: true to bypass. Successful mutations invalidate that API's cached reads.

Built-in API catalog

You don't need to hunt for spec URLs. search_catalog searches two sources:

1. A curated list of verified free/popular APIs: GitHub, GitLab, Stripe, OpenAI, Wikipedia, Open-Meteo (weather, no key), a countries GraphQL API, httpbin and the Swagger Petstore. Entries carry working spec URLs, base-URL overrides and auth hints (e.g. "optional GITHUB_TOKEN").
2. The APIs.guru directory - 2500+ community-indexed OpenAPI specs (Google, AWS, Microsoft, Twilio, NASA, ...), fetched once per session and searched locally.

search_catalog(query="weather forecast")
  -> [{"name": "open_meteo", "spec": "https://...forecast.yml", "base_url": "https://api.open-meteo.com", ...}]
load_api(spec="https://...forecast.yml", name="open_meteo", base_url="https://api.open-meteo.com")
execute(operation_id="open_meteo.get_v1_forecast", params={"latitude": 52.52, "longitude": 13.41, "hourly": "temperature_2m"})

The catalog is discovery-only: it returns spec URLs, never loads or executes anything itself, so the security guard still applies to everything you load from it.

Installation

The server runs in any MCP host via uvx - no manual install needed, the package is fetched from PyPI automatically (add [all] for GraphQL/gRPC/SOAP support):

{
  "mcpServers": {
    "universal-connector": {
      "command": "uvx",
      "args": ["universal-connector-mcp"],
      "env": { "UCMCP_ALLOWED_HOSTS": "api.github.com" }
    }
  }
}

From source (development): pip install -e ".[all,dev]" and use "command": "universal-connector-mcp" instead. Extras: graphql, grpc, soap, keyring, all, dev; the core install supports OpenAPI/REST only.

Cursor

One click via the badge above, or add the JSON block to .cursor/mcp.json in your project (shared with your team) or ~/.cursor/mcp.json (personal, all projects). See examples/mcp.json for a full config with credentials.

Claude Desktop

Add the same mcpServers block to claude_desktop_config.json (Settings > Developer > Edit Config).

Claude Code

claude mcp add universal-connector -- uvx universal-connector-mcp

VS Code (Copilot)

Add the server under "servers" in .vscode/mcp.json:

{
  "servers": {
    "universal-connector": { "command": "uvx", "args": ["universal-connector-mcp"] }
  }
}

Windsurf / Cline / others

All major MCP hosts accept the same mcpServers block shown above in their respective config files (~/.codeium/windsurf/mcp_config.json, Cline's MCP settings, etc.).

AI agents installing this server for a user: follow llms-install.md.

Preloading APIs

Point UCMCP_APIS_CONFIG at a YAML file to auto-load APIs at startup - see examples/apis.example.yaml.

Managing APIs from chat

You never edit config files to manage APIs - just tell your agent:

• "Connect the Stripe API" - the agent finds it in the catalog and loads it.
• "What APIs are connected?" - list_apis shows them.
• "Forget GitHub" - unload_api removes it (and from the remembered state).

When an API needs credentials, load_api tells the agent exactly which environment variable to set (e.g. STRIPE_API_KEY), whether it is already configured, and the agent relays copy-pasteable instructions - you add the variable to the env block of your MCP config and restart. Secrets are never typed into the chat.

Session persistence

The server remembers which APIs you loaded (their spec locations - never credentials or response data) in UCMCP_STATE_FILE and restores them automatically on the next start, so the agent can pick up right where it left off. Set UCMCP_STATE_FILE=off to disable.

Supported protocols

Protocol	Spec source	Notes
OpenAPI / Swagger	OpenAPI 3.x or Swagger 2.0 (JSON/YAML), URL/file/raw	Core install. Local $ref resolution, all HTTP methods.
GraphQL	Introspection JSON or SDL	pip install '.[graphql]'. Auto-generates selection sets; execute accepts a fields override.
gRPC	Server reflection (grpc://host:port)	pip install '.[grpc]'. Unary-unary methods; reflection must be enabled server-side.
SOAP	WSDL (URL/file/raw)	pip install '.[soap]'. One body object parameter per operation.

Each loaded operation gets an id namespaced as <api>.<operation> (e.g. github.repos_get).

Example session

More walkthroughs (weather, GitHub with auth, GraphQL, parallel multi-API workflows, internal APIs): docs/EXAMPLES.md

search_catalog(query="github")
load_api(spec="https://raw.githubusercontent.com/github/rest-api-description/main/descriptions/api.github.com/api.github.com.json", name="github")
search_operations(query="list repositories for user", api="github")
get_operation(operation_id="github.repos_list_for_user")
execute(operation_id="github.repos_list_for_user", params={"username": "torvalds"},
        extract=["*.name", "*.stargazers_count"])

GraphQL with field selection:

load_api(spec="https://countries.trevorblades.com/", protocol="graphql", name="countries")
execute(operation_id="countries.country", params={"code": "US", "fields": "name capital currency"})

Chaining (feed one result into the next; wrap steps in a nested list to run them in parallel):

execute_chained(steps=[
  {"operation_id": "github.repos_list_for_user", "params": {"username": "torvalds"}, "save_as": "repos"},
  {"operation_id": "github.repos_get", "params": {"owner": "torvalds", "repo": "${repos.data.0.name}"},
   "extract": ["description", "stargazers_count"]}
])

Configuration

All settings are environment variables prefixed with UCMCP_:

Variable	Default	Description
UCMCP_ALLOWED_HOSTS	(empty)	Comma-separated extra hosts allowed for outbound calls. Prefix with . for suffix matches.
UCMCP_DENIED_HOSTS	(empty)	Comma-separated hosts always blocked (wins over allow).
UCMCP_ALLOW_ALL_HOSTS	false	Disable the allowlist entirely (not recommended). Does not disable private-IP blocking.
UCMCP_BLOCK_PRIVATE_IPS	true	Block outbound calls that resolve to private/loopback/link-local/cloud-metadata IPs (SSRF protection).
UCMCP_MAX_REDIRECTS	5	Max HTTP redirects to follow; every hop is re-checked against the guard.
UCMCP_MAX_RESPONSE_BYTES	100000	Response body cap sent back to the agent.
UCMCP_HTTP_TIMEOUT	30	Per-request timeout (seconds).
UCMCP_MAX_RETRIES	2	Retries on transient HTTP failures (429/502/503/504).
UCMCP_CACHE_TTL	60	Seconds to cache successful GET/query responses (0 disables).
UCMCP_AUDIT_ENABLED	true	Toggle audit logging.
UCMCP_AUDIT_FILE	(none)	Append audit entries to this file (JSON lines).
UCMCP_USE_KEYRING	false	Also resolve secrets from the OS keyring.
UCMCP_APIS_CONFIG	(none)	Path to a YAML file of APIs to preload at startup.
UCMCP_STATE_FILE	~/.universal-connector-mcp/state.json	Where loaded APIs are remembered between restarts (spec locations only - never secrets or data). Set to off to disable.

Credentials are looked up by convention from <API_NAME>_TOKEN, <API_NAME>_API_KEY, <API_NAME>_CLIENT_ID / <API_NAME>_CLIENT_SECRET (OAuth2 client credentials), etc.

Development

pip install -e ".[all,dev]"
pytest          # run the test suite
ruff check .    # lint

The test suite (60+ tests) and lint run in CI on Ubuntu and Windows with Python 3.10 and 3.12 on every push (.github/workflows/ci.yml); tagging v* builds and publishes to PyPI via trusted publishing (.github/workflows/release.yml).

Contributions welcome - see CONTRIBUTING.md. Security reports go through private reporting.

Releases are automated: tagging v* publishes to PyPI via trusted publishing (see docs/RELEASING.md).

Security model

• Outbound allowlist - by default only hosts of explicitly loaded specs are reachable. Extend/limit via UCMCP_ALLOWED_HOSTS / UCMCP_DENIED_HOSTS.
• SSRF protection - requests that resolve to private, loopback, link-local, reserved or cloud-metadata addresses are blocked (including spec fetches, GraphQL introspection and SOAP imports). Every redirect hop is re-validated. Reaching an internal address requires an explicit UCMCP_ALLOWED_HOSTS entry.
• Secret handling - credentials come from environment variables or the OS keyring, are injected only at request time, and are redacted from audit logs and errors.
• Response caps - responses are truncated to a configurable byte limit to protect the context window.
• Audit log - method, host, path and status of every outbound call (never secrets or bodies) are recorded.

License

MIT