Count documents

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

No annotations are provided, so the description carries the full burden. It discloses a useful behavioral trait: this tool is cheaper than a search. However, it does not explicitly state that the operation is read-only, non-mutating, or what the response format is. For a simple count operation this is modest but not fully complete.

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 a single sentence that earns its place: it states what the tool does and when to use it. No wasted words and the key advantage is front-loaded.

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 count tool, the description plus schema covers the purpose, the query semantics, and the main usage condition. It does not explicitly state that the return value is a count, but that is strongly implied by the name, title, and described behavior. The absence of an output schema is not a serious gap here.

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 both parameters (index and query) are already documented in the schema. The description only reinforces the role of the query clause ('matching a query') without adding new detail. Baseline 3 is appropriate when the schema handles parameter documentation.

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 clearly states a specific action ('Count documents matching a query') and the resource. It also distinguishes itself from sibling tools like es_search by noting it is 'cheaper than a search' when only the total matters, so an agent can tell it apart without opening 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 explicitly says when to prefer this tool: 'Cheaper than a search when only the total matters.' This gives a clear condition for choosing it over a full search. It could be more explicit by naming alternatives like es_search, but the guidance is still clear and actionable.

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