Mimir

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"Mimir guarda el pozo de la sabiduría: aconseja a Odín cuando le falta contexto. Tu router MCP hace lo mismo con el LLM."

Mimir is a declarative MCP router built on FastMCP 3.x. Drop a plugin.toml next to any MCP server and Mimir discovers it, mounts it under its own namespace, scopes its credentials, filters its tools, and exposes the union to your client (Claude Desktop, an agent in a loop, anything that speaks MCP over stdio).

What sets Mimir apart from other MCP aggregators:

• Declarative plugin contract — every plugin ships its own plugin.toml describing identity, runtime, security, requirements. No central config to keep in sync.
• Inventory separated from plugins — operators describe their infrastructure in inventory/*.yaml (hosts, services). Plugins ask the router "give me hosts of type X" — they never hardcode IPs or hostnames.
• LLM-guided onboarding — when a plugin needs hosts or credentials the operator hasn't supplied, the router exposes a setup_<plugin>() meta-tool. The LLM walks the operator through what's missing, conversation by conversation.
• Layered security — manifest quarantine, audit log, scoped credential vault, profile gate, tool whitelist/blacklist, and cross-plugin env scoping in subprocess. See docs/security-model.md.

Quick install

git clone https://github.com/CTRQuko/mimir-mcp
cd mimir-mcp
uv sync
uv run python router.py --dry-run

The dry-run prints what Mimir sees: inventory, discovered plugins, skills/agents. Without configuration it serves only meta-tools — that's intentional. Drop your first plugin under plugins/ and re-run.

Hello world — the minimal plugin

Look at examples/echo-plugin/ to see the full contract in ~30 lines. To mount it:

ln -s "$(pwd)/examples/echo-plugin" plugins/echo
uv run python router.py --dry-run

Output:

[mimir] router — profile: default
[mimir] Core: inventory, secrets, audit, memory(noop)
[mimir] Inventory: 0 hosts, 0 services
[mimir] Plugins discovered: 1
[mimir] Skills: 0  Agents: 0

Now the client sees echo_echo and echo_reverse alongside the router_* meta-tools.

How it compares

There are several MCP aggregators in the wild. Mimir occupies a specific slot:

Documentation

• docs/naming-guide.md — canonical naming conventions for plugins, repos and tools.
• docs/plugin-contract.md — full reference for the plugin.toml schema.
• docs/inventory-schema.md — the YAML format operators use to declare hosts and services.
• docs/security-model.md — the seven security layers in detail.
• docs/ARCHITECTURE.md — how the router, core modules and plugins fit together.
• docs/INSTALL.md — installation paths beyond the Quick install above.
• docs/operator-notes/ — notes from one real deployment (the author's homelab). Useful as a worked example; not part of the public contract.

Status

Mimir is a working framework with a 280+ test suite covering the core modules, the loader, the router wiring, the security model, the example plugin and the cutover manifests. It is being used in production by the author against a real homelab. The branch refactor/generify-naming (this code) is not yet published; the public release is gated on the cutover described under docs/operator-notes/cutover/.

Project goals (and non-goals)

Goals:

• A small, readable router that anyone can audit in an evening.
• Plugins as truly independent MCP servers — usable standalone or mounted.
• Onboarding that an LLM can carry the operator through.
• Security defaults that the operator can reason about.

Non-goals:

• A full PaaS or sandbox. Mimir trusts the OS for process isolation; layer 5 tier 2 (filesystem/network/exec interceptors) is explicitly deferred until a real sandbox lands.
• A web UI. CLI + LLM are the supported control planes.
• Replacing FastMCP. Mimir is built on top of it.

License

MIT. See LICENSE.

Acknowledgements

• The Model Context Protocol team at Anthropic for the standard.
• FastMCP for the Python building blocks.
• The author's prima Claude, for asking "is this for one homelab or for an ecosystem?" at the right moment.