digi-mouse-search

An MCP server that searches electronic components across DigiKey and Mouser. Each distributor can be queried on its own or both together, with offers for the same part number merged into a single entry so prices can be compared.

Tools

search_parts takes a sources list. Omitting it searches every configured distributor; passing ["mouser"] searches that one alone. Results are merged by part number by default, with a cheapest_at_quantity comparison; pass merge=false to keep each distributor's results in a separate list.

If one distributor fails, is unconfigured, or is out of quota, the others still return results and the failure is reported under errors.

Setup

mise install
mise run install
mise run test

Credentials come from the environment:

# DigiKey: register an app at developer.digikey.com with Product Information enabled
export DIGIKEY_CLIENT_ID=...
export DIGIKEY_CLIENT_SECRET=...

# Mouser: request a Search API key from mouser.com/api-hub
export MOUSER_API_KEY=...

Only the credentials of the distributors you actually want are needed. A source without credentials is reported as unconfigured rather than failing the search.

Getting credentials

DigiKey. A personal developer app only ever gets sandbox access, and the sandbox returns synthetic data. For real stock and pricing you need a Production app, which lives under an Organization:

1. Sign in at developer.digikey.com with your DigiKey account.

2. Open Organizations on the nav bar and create one if you are not already a member.

3. Under Operations, choose Production Apps, then Create Production App.

4. Enable Product Information for the app.

5. Open the app to copy its Client ID and Client Secret.

The OAuth callback field is only used by three-legged OAuth. This server uses the two-legged client credentials flow, so the callback is never redirected to; https://localhost satisfies the form.

Sandbox and production credentials are not interchangeable. Sandbox credentials work only against sandbox-api.digikey.com, which is what DIGIKEY_SANDBOX=true selects.

Mouser. Request a Search API key at mouser.com/api-hub. It is a single key, sent as a query parameter, and arrives by email.

MCP client configuration

{
  "mcpServers": {
    "digi-mouse-search": {
      "command": "/path/to/digi-mouse-search/.venv/bin/python",
      "args": ["-m", "digi_mouse_search"],
      "env": {
        "DIGIKEY_CLIENT_ID": "...",
        "DIGIKEY_CLIENT_SECRET": "...",
        "MOUSER_API_KEY": "..."
      }
    }
  }
}

Rate limits

Both distributors grant roughly a thousand calls per day, so every request is budgeted. Per-second and per-minute windows are enforced by waiting; the daily window is a hard stop that reports an error instead, since a caller cannot usefully wait out a quota that resets at midnight. The daily counter is persisted, so restarting the server does not reset it.

Defaults:

Every value is configurable per provider, either by environment variable or by a TOML file. Use none, off, unlimited or 0 to disable a window:

export DIGIKEY_RATE_PER_DAY=250
export DIGIKEY_RATE_PER_MINUTE=30
export MOUSER_RATE_PER_SECOND=none
export MOUSER_RATE_BURST=5
export MOUSER_RATE_MAX_WAIT=30

Or point DMS_CONFIG at a file, see config.example.toml. Environment variables override the file, so a client launch command can adjust a limit without editing configuration on disk.

Cached responses are served without spending budget. source_status reports what remains for the day.

Other settings

Architecture

classDiagram
    class MCPServer {
        search_parts(keyword, sources, merge)
        part_details(part_number, sources)
        source_status()
        clear_cache(source)
    }
    class SearchService {
        +providers: dict
        +limiters: dict
        +resolve_sources(sources)
        +search(...) SearchResult
        +details(...) list~Part~
    }
    class Provider {
        <<abstract>>
        +name: str
        +configured: bool
        +search(...) list~Part~
        +details(...) Part
        #_cached_request(...)
    }
    class DigiKeyProvider {
        -_token: str
        -_access_token()
        -_manufacturer_filter_id(name)
        -_pick_variation(product)
    }
    class MouserProvider {
        -_parse_response(response)
        +parse_price(raw)
    }
    class RateLimiter {
        +acquire()
        +remaining_today()
    }
    class Cache {
        +get(key)
        +set(key, provider, value, ttl)
        +get_daily_usage(provider, day)
        +increment_daily_usage(provider, day)
    }
    class Part {
        +source, mpn, manufacturer
        +stock, price_breaks, specs
        +unit_price_at(quantity)
    }
    class MergedPart {
        +mpn
        +offers: list~Part~
        +sources
    }

    MCPServer --> SearchService
    SearchService --> Provider
    SearchService --> RateLimiter
    SearchService --> Cache
    Provider <|-- DigiKeyProvider
    Provider <|-- MouserProvider
    Provider --> RateLimiter : acquire before call
    Provider --> Cache : read before spending budget
    RateLimiter --> Cache : persist daily counter
    Provider --> Part : produces
    MergedPart o-- Part : groups offers by part number

Request flow for one provider call:

sequenceDiagram
    participant C as MCP client
    participant S as SearchService
    participant P as Provider
    participant K as Cache
    participant L as RateLimiter
    participant A as Distributor API

    C->>S: search_parts(keyword, sources)
    S->>S: resolve_sources
    par each source
        S->>P: search(keyword)
        P->>K: get(key)
        alt cached
            K-->>P: payload
        else not cached
            P->>L: acquire()
            alt budget available
                L-->>P: ok
                P->>A: HTTP request
                A-->>P: response
                P->>K: set(key, payload)
            else daily quota spent
                L--)P: RateLimitExceeded
            end
        end
        P-->>S: parts or error
    end
    S->>S: merge by part number
    S-->>C: results plus per source errors

Notes on the two APIs

DigiKey uses OAuth2 client credentials. The token lasts ten minutes and is cached in memory; requests need the client id header alongside the bearer token. Filters are expressed as opaque ids, so a manufacturer name is first resolved through the manufacturers endpoint.

Mouser uses an API key passed as a query parameter and answers with HTTP 200 even when the request failed, putting the failure in an Errors array. The adapter treats that array as authoritative. Prices arrive as localized display strings rather than numbers.

Parametric specifications have no shared vocabulary between the two distributors, so they are passed through as a name/value map rather than normalized into a common schema.

Claude Code was used in the making of this tool.