message-agent

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

The description discloses a key behavioral trait beyond annotations: it returns a NEW task_id while the original task remains terminal, and instructs monitoring the new ID. This is valuable context that annotations (readOnlyHint, idempotentHint) do not fully convey. No contradiction with 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 bold labels (Returns, When to call, Find task_id). Every section adds useful information with no fluff, making it easy to scan while remaining informative.

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 tool with 4 parameters, no output schema, and rich annotations, the description covers all essential aspects: purpose, when to use, how to locate task_id, and return behavior. It does not need to explain cwd/timeout since those are fully documented in the schema.

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%, so the baseline is 3. The description adds meaning by explaining that the task_id should be picked from terminal tasks and that the default message 'continue' resumes exactly where it left off, which supplements the schema's parameter descriptions.

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 uses a specific verb-resource pair: 'Send a follow-up message to an existing agent session' and clarifies that it resumes the session. This clearly distinguishes it from sibling tools like launch-super-coder (new agent) and cancel-agent (cancel).

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 includes an explicit 'When to call' section, specifying terminal agent states (completed/failed/rate-limited) and follow-up instructions. It does not explicitly state when not to call or name alternatives, but the context is clear enough to guide selection.

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