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

Annotations already cover the safety profile (read-only, idempotent, non-destructive, open-world). The description adds useful behavioral context by naming the data sources (CNMV entity search and ISIN register) and specifying that the result includes matching entities plus the CNMV entity page URL. It does not discuss rate limits or authentication needs, but those are secondary for this read-only lookup.

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?

Three concise sentences: the first states the purpose, the second states the return values, and the third routes the agent to downstream tools. The purpose and output are front-loaded with 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?

For a simple read-only resolver with no output schema, the description explains what is returned (matching entities with name + NIF, plus the CNMV entity page URL) and how to use the result. Annotations carry the safety profile, and the description covers the remaining agent-facing context.

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%, so the schema already documents both parameters with examples. The description adds that either an issuer name or an ISIN can be supplied and both resolve to the same NIF, but it does not clarify behavior when both parameters are provided or add formatting constraints beyond the schema. Baseline 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 states a precise verb and transformation: resolve a Spanish-market issuer name or ISIN to the NIF used by CNMV registers. It distinguishes the tool from generic entity resolvers by naming the CNMV entity search and ISIN register, and it names sibling tools that consume the output (cnmv_search_filings, cnmv_annual_reports).

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 clearly places the tool in a workflow: use it to obtain a NIF, then use that NIF with cnmv_search_filings or cnmv_annual_reports. It does not state explicit exclusions or compare against alternative resolver tools such as resolve_entity, but the intended context is unambiguous.

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