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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description's extra value is the disclosure that filtering happens server-side against a pre-built index and that results are capped at the top 20. The result cap is genuinely useful behavioral context an agent cannot get from the annotations, though it doesn't say what happens when a query exceeds 20 matches or how the index relates to forVersion.

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 with no wasted words; the primary purpose is front-loaded before the execution detail about server-side filtering and result count. Every sentence carries information the agent needs.

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 and no annotation detail on returns, the description should say what a match record looks like, and it does not. The required forVersion parameter is also left unexplained, which is the largest omission for a two-parameter tool.

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 0%, so the description must carry parameter meaning. It does explain the query parameter reasonably well by enumerating what fields are matched (name, signature, keyword), but the required forVersion parameter is never mentioned at all — an agent has no idea what format a version string takes or why it is mandatory. Only half the parameters are covered at low schema support.

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?

"Find stdlib functions by name, signature, or keyword" names a specific verb and resource and scopes the search domain to stdlib functions, which implicitly contrasts with the similarly named docs_search sibling. It stops short of explicitly differentiating itself from docs_search or stdlib_module, so an agent must infer the boundary from the resource noun alone.

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 description implies usage through the three lookup modes (name, signature, keyword), which suggests reaching for this tool when you have any of those handles. However, it never states when to prefer it over docs_search or stdlib_module, and there are no exclusions or prerequisites given.

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