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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, and the description is consistent with them. Beyond that it discloses a 60-second cache TTL and characterizes the call as 'a MAT catalog read, like the list', which is real behavioral context an agent cannot get from the annotations.

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 purpose statement is front-loaded well, but the description then restates itself: 'every skill its card declares' appears in the first sentence and is re-listed verbatim in the second, along with duplicated coverage of capabilities and protocol version. The duplication costs space without adding information.

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?

With no output schema, the description carries the return-value burden and does enumerate the response shape (skills, capabilities, protocol version, docs/icon URLs, first-seen timestamp, registries and licenses). For a 3-parameter read tool with full schema coverage this is sufficient, though auth/licensing nuance for api_pass is left to the schema.

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 all three parameters (chave, api_pass, retry_key) are already documented in the schema. The description only reiterates that the key comes from a2a_agent_search, adding no syntax or format detail beyond the schema; baseline 3 applies.

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?

It states a specific verb and resource ('Read one A2A agent') and enumerates the salient contents (skills, capabilities, protocol version, health, registries). The final clause 'The same row as the list plus what the card declares' cleanly positions it against the sibling a2a_agent_search (the list).

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?

'Take the key from a2a_agent_search' gives a concrete prerequisite and implicitly routes the agent: use search to obtain the chave, use this tool to fetch the single record. There is no explicit when-not guidance, but the list-vs-single split is clear from context.

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