Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover read-only and non-destructive behavior. The description adds value by specifying the exact response shape, which the annotations do not provide. It does not disclose sorting order or limit application, but the schema covers limit defaults.

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?

Two sentences with zero fluff. The first states the core purpose, the second provides a compact, concrete output example. Everything earns its place.

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 supplies the response shape, and the schema covers all optional parameters. The tool is simple enough that an agent can call it correctly. Minor gaps like explicit sorting order are implied by 'top'.

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 description coverage is 100%, so the schema fully documents all three parameters. The description's output example indirectly clarifies what 'sources' means via the dimension key, but does not add direct parameter-level semantics beyond the schema.

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?

The description clearly states the tool returns top traffic sources by visitors for a site, with an explicit example dimension (visit:source) and metrics (visitors, bounce_rate). This makes it easily distinguishable from siblings like top_countries, top_pages, and top_goals.

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?

No guidance is given on when to use this tool versus the many similar top_* siblings or query_stats. The agent is left to infer selection from the name alone, with no mention of alternatives or conditions.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.