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

Annotations already carry the safety profile (readOnlyHint, idempotentHint, non-destructive), so the bar is lower. The description adds genuine value beyond annotations: the guarantee that 'content is never machine-translated' and the return format ('matching descriptors with MeSH IDs and labels'). It does not cover pagination or error behavior, but for a search tool with strong annotation coverage, this is solid.

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 well-structured: core purpose first, then use cases, then the critical language caveat, then return format. It is compact with no wasted sentences. The bullet list slightly rephrases the opening line, but each bullet adds a distinct usage angle, so it 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?

Given the presence of an output schema, annotations covering safety, and 100% schema param coverage, the description is complete. It states what is searched, why an agent would use it, the one non-obvious behavior (no machine translation), and what results contain. Nothing an agent needs to invoke it correctly is missing.

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 baseline is 3. The description reinforces the language parameter's special behavior (official translations only, e.g., Portuguese), but that nuance is already documented in the schema's language property. The description adds no new parameter semantics beyond what the schema provides, so a 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?

The opening sentence states a specific verb and resource: 'Search for MeSH (Medical Subject Headings) descriptors.' The bulleted use cases (indexing literature, PubMed searches, controlled vocabulary) further anchor what the tool does and differentiate it from domain-specific siblings like cid10_search or atc_lookup without needing to open their schemas.

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 gives clear context for when to use the tool via three concrete use cases, but it never names alternatives or states when NOT to use it (e.g., no routing to mesh_descriptor for looking up a specific known MeSH ID). This meets 'clear context, no exclusions,' which fits a 4.

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