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

The readOnlyHint annotation already signals this is a safe read operation. The description adds behavioral context beyond that: it returns grouped categories with type and description, and emphasizes that field paths differ across endpoints. This is useful but does not describe the exact output structure; however, an output schema exists, so the return format is already documented. The description supplements annotations adequately.

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 two sentences with no filler. The core purpose is front-loaded, followed immediately by the usage context and the rationale for why this tool exists. Every sentence earns its place, and the structure makes it easy for an agent to quickly grasp the tool's role.

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 one-parameter discovery tool with an output schema already present, the description is fully complete. It explains what the tool does, when to use it, and why it's necessary, leaving no missing information that an agent would need to make a correct call. The presence of the output schema covers return values, so no further explanation is required.

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 input schema provides 100% coverage for the single 'endpoint' parameter, including an enum of valid values and a description. The tool description adds a rationale for why the endpoint parameter is needed (to identify the correct field paths), but does not provide additional syntax or format details beyond the schema. Given full schema coverage, the baseline score of 3 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 states the tool's purpose: 'Return the searchable field paths for an openFDA endpoint, grouped by category with type and description.' It identifies a specific verb (return), resource (field paths), and the grouping/type/description outcome. This distinguishes it from sibling search/count tools, which operate on data rather than metadata.

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 provides explicit when-to-use guidance: 'Use before constructing a search query to find the correct dotted field path.' It also explains why (field paths differ per endpoint and are not discoverable from the schema). It does not explicitly name an alternative tool, but the context of 'before constructing a search query' implies the correct timing and alternative search tools. This is clear usage guidance but lacks an explicit exclusion statement.

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