Get A2A Agent Card

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

Annotations already indicate readOnlyHint, idempotentHint, and non-destructiveness. The description goes further by documenting error messages for unreachable URLs, invalid formats, and 404 responses, as well as the expected return structure and A2A protocol context. This is meaningful behavioral disclosure beyond 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 description is well-structured with clear sections for Args, Returns, Examples, and Error Handling, and it front-loads the core purpose. The three usage examples are somewhat repetitive, but they are concise and reinforce the intended invocation pattern.

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?

The tool has one simple parameter, no output schema, and comprehensive annotations. The description fully compensates for the missing output schema by enumerating the expected response fields, and it covers errors, protocol context, and practical usage. Nothing essential is missing for an agent to call this tool 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?

The schema already fully documents agentCardUrl with 100% coverage, so the baseline is 3. The description adds value by explaining that the endpoint is 'typically at /.well-known/agent-card.json' and providing concrete example URLs, which helps the agent construct valid parameter values.

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 verb and resource: 'Retrieve an agent's card containing metadata and capability information.' It also names the sibling alternative for sending messages, so the tool is clearly distinguished from a2a_send_message and the other siblings.

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?

Usage guidance is explicit with 'Use when' examples such as 'What can this agent do?' and a 'Don't use when' clause that routes to a2a_send_message instead. This gives an agent clear decision criteria for selecting this tool versus its siblings.

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