cancel_thread

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

Goes well beyond the annotations, which only declare readOnly=false, destructive=false, idempotent=true. The description clarifies that despite the 'cancel' verb nothing is destroyed ('never deletes posts'), specifies exactly what survives (confirmed URLs, uncertain evidence), and adds a hard precondition on active sends. This is precisely the non-obvious behavioral context an agent needs.

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?

Three short sentences, front-loaded with the core action and then layering retention guarantees and the precondition. Little waste, though the final precondition sentence reads slightly awkwardly ('before cancellation can be accepted').

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 an output schema present, return values need no explanation, and the annotations carry the safety profile; the description fills the remaining gap with retention semantics and preconditions. Adequate for a single-parameter mutation, though the run_id parameter remains entirely undocumented.

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 description coverage is 0% and the single run_id parameter is never mentioned in the description, so it adds no meaning for the parameter. However, run_id is a conventional identifier and its role is reasonably inferable from the 'thread' context, keeping this near the minimum-viable baseline.

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 and resource: 'Cancel remaining thread segments locally.' This clearly distinguishes it from continue_thread and prepare_thread. It stops short of naming a sibling explicitly, but the action and scope are unambiguous.

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?

Provides a precondition ('An active send must finish before cancellation can be accepted'), which is useful usage context, but never states when to prefer this over alternatives like cancel_queued_action or simply letting a run complete. Usage is implied rather than directed.

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