fathom_get_current_visitorsLive visitors on a site right now: the total, and with detailed true the top 150 pages (hostname, pathname, total) and top 150 referrers. GET /current_visitors.
| Name | Required | Description | Default |
|---|---|---|---|
| site_id | Yes | The site id, the same string as in the tracking code (e.g. CDBUGS). fathom_list_sites lists them. | |
| detailed | No | true = also the top pages and referrers (default false: only the count). |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safety profile (readOnlyHint, openWorldHint), and the description adds the return shape and the underlying GET /current_visitors endpoint. It omits auth/rate-limit context, but the return structure disclosure is meaningful for a tool with no output schema.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
A single dense sentence with the core purpose front-loaded and no wasted clauses; the detailed=true behavior is tacked on exactly where it is needed.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
With no output schema, the description does the necessary work of describing the total plus the detailed page/referrer breakdowns. Referrer fields are not enumerated and no freshness/refresh semantics are given, but an agent has enough to call it correctly.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is already 100%, but the description adds real value beyond the schema by spelling out what detailed=true returns (top 150 pages with hostname/pathname/total, plus top 150 referrers) including the 150 cap, which the schema does not state.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb and resource with scope: live visitors on a site right now. The real-time framing clearly separates it from the historical aggregation sibling without needing to name it.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The phrase 'right now' implies the real-time use case versus fathom_get_aggregation for historical data, but the alternative is never named and no when-not-to-use condition is given. Usage is inferable but not explicit.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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