irrationalagent/glean_mcp

Installation

git clone https://github.com/irrationalagent/glean_mcp

cd glean_mcp

python3 -m venv venv

source venv/bin/activate

pip3 install -e .

Run (Standalone)

glean-mcp

Configure for Use w/ Claude CLI

Add the following to .mcp.json, making sure to specify the right path:

    "mcpServers": {
      "glean": {
        "command": "/some/path/glean_mcp/venv/bin/glean-mcp",
        "args": []
      }
    }

start claude: claude

List MCP servers: /mcp

Available Tools

This MCP server provides three main tools for interacting with Mozilla's Glean telemetry system:

1. list_apps_tool

Lists all available Glean applications with their identifiers.

Parameters: None

Returns: JSON array with app metadata including:

• v1_name: The v1 identifier for the app (use this with other tools)
• app_name: Display name
• app_id: Application ID
• bq_dataset_family: BigQuery dataset family name
• canonical_app_name: Canonical name
• document_namespace: Documentation namespace

Example usage:

> list all glean apps

2. search_metrics

Search for Glean metrics across all applications using free-text queries.

Parameters:

• query (required): Search terms (e.g., "startup time", "default browser")
• app_hint (optional): App identifier to bias results (e.g., "fenix", "firefox_ios")
• limit (optional, default=25): Maximum number of results

Returns: JSON array of matching metrics with:

• id: Metric identifier
• name: Metric name
• category: Metric category
• type: Metric type (counter, boolean, string, event, etc.)
• app: Application name
• description: What the metric measures
• send_in_pings: Which pings include this metric
• url: Link to Glean Dictionary page

Example usage:

> search for metrics about startup time in fenix
> find metrics tracking default browser on firefox_ios

3. get_metric_details

Get detailed information about a specific metric including full definition, data reviews, and extra keys.

Parameters:

• v1_name (required): App identifier (e.g., "fenix", "firefox_ios")
• metric_name (required): Full metric name (e.g., "collections.save_button")

Returns: JSON object with complete metric details including:

• latest_definition: Full metric definition with:
  • bugs: Related bug URLs
  • data_reviews: Data review links
  • description: Detailed description
  • lifetime: Metric lifetime (ping, application, etc.)
  • type: Metric type
  • extra_keys: Event metadata (for event metrics)
  • data_sensitivity: Data sensitivity classifications
  • notification_emails: Contact emails
  • And more...

Example usage:

> get details for the metric app.default_browser on firefox_ios
> show me the full definition of collections.save_button on fenix

Example

> please find the probe on firefox_ios that tracks whether the browser is set to default

⏺ I'll search for Firefox iOS probes related to default browser status.

⏺ glean - search_metrics (MCP)(query: "default browser", app_hint: "firefox_ios", limit: 25)
  ⎿  [                                                                                                                           
       {
         "id": "default_browser_card.dismiss_pressed",
[...]

⏺ I found the probe that tracks whether Firefox iOS is set as the default browser:

  app.default_browser
  - Type: boolean
  - Description: Is Firefox the default browser

  Additionally, there are related probes that provide context:

  app.opened_as_default_browser
  - Type: counter
  - Description: Counts the number of times the app is opened from an external link, implying the client has Firefox set as a
  default browser. Currently this is the most accurate way of measuring how often Firefox is set as the default browser.

  app.last_opened_as_default_browser
  - Type: datetime
  - Description: The date of when the app was last opened as default browser.

  The app.default_browser boolean probe is the direct indicator, while app.opened_as_default_browser is noted as being the most
  accurate measurement method since it tracks actual usage as the default browser rather than just the setting state.