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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds the cost signal ("cheap") and the key payload property ("minimal metadata, no body") that an agent needs to judge whether a second call is warranted. Return field detail is unnecessary because an output schema exists.

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?

Three short clauses, front-loaded with what the tool returns and costs, then usage, then the alternative. No sentence is 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?

For a simple two-parameter read with full schema coverage, an output schema, and complete annotations, nothing an agent needs to call 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 coverage is 100%, so baseline is 3, but "id-based lookup" meaningfully disambiguates the document_id parameter from slug-based access in the presence of the kb_documents_get_by_slug sibling. The tenant_slug fallback behavior is left entirely to the schema.

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?

"Cheap id-based lookup returning minimal metadata (no body)" states a specific verb, the identifier type, and the output scope in one clause. It is immediately distinguishable from kb_documents_get (full body) and kb_documents_get_by_slug (slug keyed).

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?

Explicitly frames the use case ("is this doc tagged right?" follow-ups after a search or list) and names the alternative plus the condition that selects it: "Use kb_documents_get when the body is needed."

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