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

Beyond the annotations (which only indicate a mutating operation), the description adds critical behavioral context: authorization is based on ownership, not task ID possession, and replying completes the task with a non-repeatable guarantee. These details significantly enhance the agent's understanding of side effects and security semantics.

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 three concise sentences, each delivering essential information: purpose, authorization constraint, and idempotency. There is no redundancy or filler, and the most critical information is front-loaded.

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 tool with only two required parameters and an existing output schema, the description covers all essential aspects: purpose, authorization, completion behavior, and repeat-reply prohibition. It is fully sufficient for an agent to determine correct usage.

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 provides complete descriptions for all three parameters (task_id, text, message_id) with 100% coverage. The description reiterates that task_id comes from a2a_get_messages and is an identifier, but this adds no new meaning beyond the schema. Baseline of 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 clearly states the tool's purpose: to answer and complete a task retrieved via a2a_get_messages. It distinguishes from sibling tools like a2a_send_message by specifying that it is for replying to tasks specifically pulled with that retrieval tool.

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 gives explicit when-to-use conditions (tasks pulled with a2a_get_messages) and when-not constraints (task not addressed to you results in not found; completed tasks cannot be answered twice). However, it does not explicitly name alternative tools, such as a2a_send_message, so it lacks direct alternative guidance.

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