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

Annotations declare readOnlyHint=true and idempotentHint=true, so the description doesn't need to repeat that information. It adds context about the tool's purpose and usage, but doesn't disclose additional behavioral traits beyond that—such as return format (though output schema exists) or error handling. With annotations covering the safety profile, the description adds value by explaining the context enum semantics and the query behavior, but it's not particularly rich in behavioral disclosure. The description doesn't contradict annotations; it's consistent with read-only/idempotent behavior.

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 concise paragraph that front-loads the primary purpose (listing field names to avoid 400 errors) and then explains the optional `query` parameter. Every sentence serves a purpose: stating the action, proscribing proactive use, and clarifying the narrowing behavior. It's not overly verbose, but it could be slightly more structured (e.g., bullets for contexts) without losing conciseness. Still, it's efficient and well-organized.

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?

Given the tool's moderate complexity (3 params, 1 fully documented via schema and output schema present), the description adequately covers what an agent needs to know: when to use it, how to refine with query, and that it covers filter/group_by/select contexts. The output schema likely explains return values, so the description doesn't need to. The only minor gap is that it doesn't explicitly state that the tool is read-only, but annotations cover that. Overall, it's complete enough for correct invocation.

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%, meaning the schema already fully documents all three parameters. The description adds minimal extra semantics beyond what the schema provides—it reinforces the purpose of `query` and describes the context enum's meaning, but these details are largely already present in the schema property descriptions. Since coverage is high, the baseline of 3 is appropriate; the description doesn't need to compensate for missing schema info but also doesn't add significant value beyond the schema.

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 — listing valid field names for an OpenAlex entity type and context (filter, group_by, or select) — with a specific verb ('list'), a specific resource (OpenAlex field names), and explicit context of use (before constructing filters/group_by). It distinguishes itself from siblings by focusing solely on field enumeration, not on searching entities or analyzing trends, which are covered by sibling tools like openalex_search_entities and openalex_analyze_trends.

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 proactively before constructing a filter or group_by to avoid invalid-field 400 errors.' It also explains the optional `query` parameter's purpose for narrowing results by name similarity and implies when not to use it (e.g., when the exact field name is known, omit query). It indirectly differentiates from siblings by focusing on field discovery, not entity retrieval or analysis.

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