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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, so the description does not need to repeat that. The description adds the behavioral trait of 'by cosine similarity', which is useful. However, it doesn't disclose potential limitations, such as behavior on unknown theatre_slug or edge cases, and with openWorldHint=true the description doesn't add much beyond the annotation.

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?

The description is one concise sentence, front-loading the core purpose and method. It avoids unnecessary detail, making it efficient for an agent to parse. Slightly more context could be added, but for the length, it is well-structured.

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?

Given the tool's complexity is low (3 params, no output schema), the description is nearly sufficient. However, it lacks explanation of what 'precursor_library' is and how event_type affects results, leaving some ambiguity for an agent deciding to invoke it. The output format is not described, but since there is no output schema, this could be a gap.

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 67%: theatre_slug is well-described with an enum, top_k has a brief description, but event_type has no description in the schema. The tool description says 'by cosine similarity' which adds meaning to the function but does not clarify event_type's role. Since coverage is moderate, the description partially compensates but not fully.

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 states the tool's purpose clearly: 'Nearest precursor_library entries for the given theatre, by cosine similarity.' It specifies the verb 'query' implicitly through the name, the resource 'precursor_library entries', and the criterion 'cosine similarity'. However, it does not differentiate from siblings like query_posture_scores, which might also be related to theatres, and the term 'precursor_library' is not explained.

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?

There is no explicit guidance on when to use this tool versus alternatives. The description implies it is for finding similar precursor entries, but does not state when to prefer it over, say, query_posture_scores or query_calibration. No mention of exclusions or conditions under which another tool would be more appropriate.

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