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

Adds real behavioral scope beyond the annotations: it explicitly limits side effects ('Does not change requirements, acceptance, delivery or payment') and gives retry semantics tied to the idempotentHint. Note a mild tension with destructiveHint=true for a message-send operation, but the description does not assert a read operation, so it is not a direct contradiction.

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?

Four compact sentences with the core action front-loaded and constraints following. No filler, though the opening sentence is dense enough that it could be split for readability.

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 mutation tool with no output schema, it covers effect scope, task-state constraints, and retry behavior. It stops short of describing success/failure responses or authentication requirements, leaving a small gap for a destructive-hinted write.

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 50%: actorId is documented in the schema and the description adds idempotency meaning for request_key ('Retry with the same request_key and exact fields'). However, body and id receive no clarification beyond their schema types, so it only partially compensates for the coverage gap.

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?

States a specific verb (Send), resource (private message), and target (the other task participant) with a precondition (after claiming). An agent can distinguish this write action from the read-side sibling list_task_messages without opening either schema.

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?

Gives concrete state-based context: 'after claiming', completed tasks remain discussable, cancelled tasks are read-only. This tells the agent when the tool applies and when it will be blocked, though it never names an alternative tool (e.g., ask_question) for a different flow.

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