Library statistics

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

The description adds meaningful behavior beyond the readOnlyHint annotation by specifying exactly what aggregate data is returned and emphasizing the whole-library scope. It also implicitly communicates a safe, lightweight overview operation. No side effects are claimed, and the description does not contradict the annotations.

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 compact and front-loaded: the first phrase states the core scope, then the sentence enumerates the contents, and the final sentence gives the use case. Every sentence adds value and there is no redundant 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 parameterless, read-only statistics tool, the description is largely complete: it enumerates the returned categories and explains when to use it. Since there is no output schema, some response-shape detail is left unspecified, but the listed contents give an agent enough confidence to invoke the tool and interpret the result.

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?

With zero parameters and 100% schema description coverage, the input schema already fully documents the calling contract. The description adds no parameter details because none are needed. The baseline of 4 for parameterless tools 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 description clearly identifies the tool as returning library-wide totals and enumerates the specific statistics included (document count, inbox count, characters indexed, tag/correspondent/document-type counts, file type breakdown). It does not use an explicit verb, but the tool name and content make the purpose unambiguous. It implies differentiation from search-oriented siblings by stressing 'whole library' and positioning it before searching.

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 states a clear usage context: it is 'a good first call to see how big the library is before searching it.' This gives an agent a concrete trigger for choosing this tool. However, it does not explicitly mention alternatives or say when not to use it, so it falls short of full routing guidance.

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