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

Annotations already cover the safety profile (readOnlyHint true, openWorldHint false). The description adds real context beyond them: results include counts, values reflect source-system spelling, and a wrongly spelled guess matches nothing rather than erroring. That last point is a genuine behavioral gotcha, though return/pagination behavior is unstated.

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 sentences with no filler, and the core purpose is front-loaded before the matching caveat. The colon construction is slightly awkward but costs nothing in comprehension.

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 read-only sampling tool with full schema coverage and no output schema, the description supplies what's needed: what comes back (values plus counts), and the matching semantics that motivate using it. Nothing essential 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 field, entity, model, and limit are all documented in the schema, including the default of 20. The description says nothing about parameters beyond 'a field', adding no meaning over structured data, so baseline 3 applies.

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?

Specific verb (Show) and resource (most common values of a field) plus the return shape (with counts). It's clearly distinct from query/search conceptually, but it never names a sibling, so an agent must infer the boundary itself.

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 note about '=' and 'in' matching exact spellings implies this tool exists to discover spellings before filtering, which is useful implied usage. However there is no explicit when-to-use statement, no 'when not to use', and no named alternative (query, search).

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