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Mikoto

Configuration

The bridge reads project-local mikoto.toml from its current working directory unless another path is passed with --config. Start from the repository example:

Terminal window
cp mikoto.example.toml mikoto.toml

The latest JSON Schema is published at the public schema URL. Editors that understand the TOML schema directive can validate fields and provide completions while the file is edited.

#:schema https://mikoto.takuk.me/schemas/mikoto.schema.json


[bridge]
id = "dev-machine"


[relay]
url = "ws://localhost:8787/bridge"


[[servers]]
id = "codex"
transport = "stdio"
command = "bun"
args = ["packages/codex-mcp/src/index.ts"]


[[servers.aliases]]
name = "local_chrome_read_start"
target = "codex.codex_chrome_read_start"

Supported Fields

Section titled “Supported Fields”
  • [bridge].id: optional bridge identity. Defaults to the local computer name.
  • [relay].url: relay WebSocket URL. Required.
  • [[servers]].id: backend MCP id used as the tool-name prefix.
  • [[servers]].transport: stdio is implemented. http is schema-supported but returns an unimplemented error in the bridge.
  • [[servers]].command: executable used to start a stdio backend.
  • [[servers]].args: optional command arguments.
  • [[servers]].cwd: optional backend working directory.
  • [[servers]].env: optional environment variables added to the MCP SDK’s default safe environment.
  • [[servers.aliases]]: optional exposed aliases that route to another exposed tool.

The bridge starts only the MCP servers listed in [[servers]]; it does not search the computer for other servers. Every configured backend starts eagerly, and bridge startup fails if any backend fails to start or list its tools.

Discovered metadata is visible through mikoto_list_bridges, and ChatGPT invokes a selected tool through mikoto_call_tool. Tool names are prefixed with the backend id, so backend tool codex_chrome_read_start from server codex becomes codex.codex_chrome_read_start.

Aliases provide a stable or shorter exposed name without changing the backend:

[[servers.aliases]]
name = "local_chrome_read_start"
target = "codex.codex_chrome_read_start"

The alias target must be a discovered, backend-prefixed tool. Alias names must also be unique across the bridge.

Relay URL And Environment Overrides

Section titled “Relay URL And Environment Overrides”

Use the local relay URL during development:

[relay]
url = "ws://localhost:8787/bridge"

Use the WARP-protected bridge hostname for a deployed relay:

[relay]
url = "wss://bridge.example.com/bridge"

MIKOTO_RELAY_URL and MIKOTO_BRIDGE_ID override the matching config fields without editing mikoto.toml.

The relay keeps its ChatGPT-facing native tools fixed as mikoto_list_bridges and mikoto_call_tool. Backend changes appear in bridge metadata rather than as new native ChatGPT tools, avoiding stale ChatGPT App tool discovery.

See Get Started for the full deployment and first-call flow. Local run commands also live in the package README files.