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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds that results are aggregation counts honoring the same filter set as search, but says nothing about output shape or whether the aggregation ignores paging/sorting — modest added context given the annotation coverage and existing 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?

Two tight sentences, front-loaded with the core behavior and then the usage relationship. No filler, though 'the related search tool' is a slightly vague referent that costs a little precision.

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?

An output schema exists, so return values needn't be explained, and the description covers purpose, filter inheritance, and pairing with the search tool. It leaves the facet's allowed values to the schema, which is acceptable given full schema coverage.

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% across the 10 parameters, so the schema already documents q, sort, facet, run_id, vintage-year bounds, etc. The description only alludes to 'one field' (the facet param) and shared filters, adding no syntax or semantics beyond the schema. Baseline 3 is appropriate.

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+resource: returns terms-aggregation counts for one field over the PitchBook funds dataset. This is distinguishable from the sibling search/item tools, though the facets purpose is conveyed mostly by the noun 'terms-aggregation counts' rather than an explicit contrast.

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?

Gives real usage guidance: 'honoring the same filters as search' and 'Use alongside the related search tool to inspect filter counts under the same query filters,' which tells the agent when this tool is the right pick. It stops short of naming the sibling (datasets_pitchbook_funds_search) explicitly or stating when NOT to use it.

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