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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely useful behavioral context beyond them: the data returned is the free/teaser portion and most numeric figures and full lists are subscription-gated, which tells the agent to expect incomplete data. It does not cover rate limits or auth requirements, hence not a 5.

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 action and scope, followed by the gating caveat and routing alternatives. Every sentence earns its place with zero filler.

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 an output schema present, return values need not be explained. The description covers scope, data-completeness limitations, and sibling routing, which is everything an agent needs to invoke this 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 description coverage is 100% and both parameters (id, url) are fully documented including the 'pass exactly one' rule. The description merely restates 'by id or url' and adds no syntax, format, or behavioral meaning beyond the schema, so baseline 3 is correct.

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 (Fetch) and resource (PitchBook investor profile) with precise scope: the free/teaser portion, enumerating the included sections (overview, contact/HQ, previews of investments, exits, co-investors). It explicitly names the sibling tools it is not (pitchbook_company, pitchbook_fund, datasets_pitchbook_investors_search), so an agent can select it without opening any schema.

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?

Names alternatives and the conditions that select them: use pitchbook_company or pitchbook_fund for other entity types, or datasets_pitchbook_investors_search for the public dataset. When-to-use and when-to-use-something-else are both explicit.

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