na_fields

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

The annotations already declare readOnlyHint=true and openWorldHint=true, covering the safety profile. The description adds valuable context that the values are 'actually accepted' and backed by 'measured evidence,' indicating empirical verification rather than mere documentation.

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 compact sentence that front-loads the core value proposition: a list of working values plus the empirical basis. It contains no filler and does not repeat information already present in annotations or schema.

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 parameterless, read-only metadata tool, the description adequately conveys what the tool returns and why it is reliable. The lack of a response format is acceptable given the tool's simplicity and supporting annotations.

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?

The tool has zero parameters, so the schema trivially covers all parameters and the description need not add parameter-level semantics. The baseline of 4 applies because there are no parameters to explain.

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 identifies the tool as a reference list of values actually accepted by the API, with examples like search items and dbname, making its purpose as a metadata/inspection tool clear. It lacks an explicit verb and does not contrast with sibling tools, but the resource and intent are unambiguous.

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 the tool should be used to discover which field values and dbnames are valid for this API, which is a natural prerequisite for search/detail calls. However, it does not explicitly state when to use this tool over alternatives or provide any exclusions.

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