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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds real value beyond that: exact/case-sensitive matching, unknown names are reported rather than erroring, free cost, and the empty-names error. It does not describe pagination or ordering beyond request order, but with annotations carrying the behavior basics a 3 reflects solid but not exhaustive disclosure.

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?

Front-loads the return contents, then the tool-selection rule, then matching, output, cost, and errors in a dense but scannable sequence. Every clause carries operational information; no 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?

There is no output schema, but the description fills that gap by naming the two return keys (fields, unknown) and explaining that unknown names are not errors. Combined with the explicit error case and free cost, an agent has everything needed to call this correctly.

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 coverage is 100% and the single parameter already documents the 1–100 item limit and an example. The description adds meaning the schema does not: matching is exact and case-sensitive, and names must be catalog names rather than search keywords. That is genuine value beyond the schema, though it does not elaborate on array ordering semantics beyond output order.

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?

States a specific verb and resource (return the full catalog entry per named field) and enumerates exactly what the entry contains: description, type, unit, source, license, attribution, refresh interval, presets. It explicitly separates itself from search_fields and list_presets, so an agent can choose it without opening sibling 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?

Provides an explicit division of labor: describe_fields is for checking units/provenance/licensing with exact names, search_fields for finding names by keyword, list_presets for bundles. It also states the matching mode (exact, case-sensitive) and the error condition, leaving nothing to inference.

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