send_message

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

No annotations, so the description carries the full burden and does so richly: turn serialization ('turns on one session never overlap'), the waiting behavior, the background return shape {session_id, state, queued}, and steer semantics including interruption of the in-flight call. This is exactly the kind of behavioral disclosure annotations would otherwise provide.

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 dense sentences, front-loaded with the core action and session_id provenance, then waiting semantics, then background, then steer. No filler; every clause carries distinct information.

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?

Comprehensive for a 6-param mutation tool with no output schema: it covers return shape, concurrency, background and steer flows. It does not mention timeout_s behavior or the structured-output schema param, both of which are documented in the schema but the description stays silent on their runtime effect.

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 already 100%, so the baseline is 3, but the description adds non-obvious semantics: background returns early and needs wait_thronglet, and steer interrupts the running turn and jumps ahead of queued messages. That sequencing relationship between steer and queued messages is not derivable from the schema alone.

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 (sends) and resource (next message into an earlier session), and ties the session_id directly to the sibling run_thronglet. An agent can tell this apart from cancel/wait/list siblings immediately.

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?

Clearly positions this as the continuation mechanism after run_thronglet and routes to wait_thronglet for background collection. Does not explicitly say when-not-to-use, but the alternative and its trigger conditions are named.

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