Send A2A Message

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

Annotations already set readOnlyHint=false and idempotentHint=false, but the description adds significant behavioral context: the tool may return an immediate message or an async task object, responses can contain multiple parts, and specific error strings are documented. This goes well beyond the structured 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?

Although longer than average, the description is well-structured with dedicated Arg, Returns, Examples, and Error Handling sections. Every sentence contributes either parameter semantics, usage guidance, async behavior, or error troubleshooting—no filler or redundancy.

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 thoroughly documents the possible return shapes (message vs. task), async workflow, error strings, and follow-up polling behavior. It also covers all three parameters and names sibling tools where relevant, making it complete for an agent to invoke 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% with descriptions for all three parameters, so the baseline is 3. The description adds value by explaining the taskId continues a conversation thread, specifying message length in the Args section, and providing realistic example parameter values that illustrate correct usage.

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 begins with a specific verb and resource: 'Send a message to an Agent-to-Agent (A2A) protocol compliant agent.' This cleanly distinguishes it from sibling tools like a2a_get_task, a2a_cancel_task, and a2a_get_agent_card, all of which have obviously different purposes.

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 provides explicit 'Use when' and 'Don't use when' guidance with concrete examples, directly naming sibling alternatives for cancellation and status checks. It also advises using a2a_get_task for polling when a task object is returned, giving the agent clear decision criteria.

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