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

Annotations already declare readOnlyHint and idempotentHint, and the description adds meaningful behavior: checking nine required fields, validating skill fields, warning on capabilities declared true, and giving a concrete example where json='{"name":"a"}' returns the eight missing fields. This goes well beyond what annotations provide.

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 core description is tight and informative, but the embedded full JSON-RPC first-call invocation is verbose and could be misread as saying validate_agent_card itself needs no arguments, contradicting the required json parameter. This structural confusion reduces clarity.

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 single-parameter, read-only validation tool with no output schema, the description covers input expectations, validation criteria, warning behavior, and an example return. An agent has enough information to call it correctly and interpret the result.

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 schema already describes the json parameter as 'The agent card JSON itself, not a URL', and the description reinforces this with 'pasted' and an example. With 100% schema coverage, the baseline is 3; the example and emphasis on pasted JSON lift it to 4.

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 specific action: validates a pasted /.well-known/agent-card.json against the nine fields A2A requires, plus each skill's id/name/description/tags. This clearly distinguishes it from sibling validators like validate_llms_txt and check_discovery_documents.

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 'FIRST CALL, needs nothing' instruction with the JSON-RPC payload guides the agent to first call the no-argument sibling no_arguments_check_this_hosts_own_discovery_documents. The word 'pasted' also clarifies that this tool takes inline JSON rather than a URL. It does not explicitly name alternatives or state when not to use it, so it falls just short of a 5.

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