Distinct values of a field

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds behavioral context: it returns occurrence counts, sorts most common first, and positions itself as reliable for vocabulary discovery. It doesn't mention pagination or what happens with high-cardinality fields, but the limit parameter with '0 = unlimited' partially covers that.

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 wasted words. The first sentence states the core behavior (distinct values, counts, ordering), and the second adds the practical use case. Information is front-loaded and every word 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?

For a read-only, idempotent tool with two parameters and no output schema, the description is nearly complete. It explains what the tool returns (distinct values with counts, sorted) and when to use it. The only minor gap is not describing the output format structure (e.g., array of objects with value/count keys), but the description's clarity compensates for the missing output schema.

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 50%: 'field' has no description, while 'limit' has a description and default. The description clarifies that the tool returns distinct values with counts, which implies the 'field' parameter is the target field. It doesn't add detail about the 'limit' parameter beyond the schema, but the schema already documents it well. The description compensates for the undocumented 'field' parameter by explaining the tool's purpose.

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 a specific verb ('catalog') and resource ('values of a field'), and clearly distinguishes itself from siblings by emphasizing occurrence counts and ordering. It also explains the practical use case (learning a categorical field's vocabulary before filtering), which makes the tool's purpose immediately clear.

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 when to use this tool: when you need distinct values with counts before filtering. It doesn't explicitly name alternatives or exclusions, but the phrase 'reliable way to learn a categorical field's vocabulary' provides clear context. Sibling names like catalog_top and catalog_count_by suggest related tools, but the description doesn't explicitly contrast them.

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