cancel_agent_run

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

Annotations already flag destructiveHint=true and idempotentHint=true, and the description adds meaningful context: the operation is audit-logged, checkpointed, and the run record is retained rather than deleted. It also states that cancellation ends the lifecycle. This adds value beyond the annotation flags without contradicting them.

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 sentences, no filler. The primary action is front-loaded, followed by conditions, alternatives, and side effects in logical order. Every sentence earns its place.

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 single-parameter tool with no output schema, the description covers all necessary context: when it can be used, failure modes, alternative actions, side effects, and return value. Nothing an agent needs to invoke it correctly is missing.

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 documents run_id with 'Run id from create_agent_run or list_agent_runs' and coverage is 100%. The description only repeats the parameter name without adding new constraints or format details, so it meets the baseline for fully-covered schema parameters.

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 opens with a specific verb and resource ('Cancel an agent run by run_id') and states the terminal state ('ending its lifecycle at cancelled'). It clearly differentiates from siblings like resume_agent_run and approve_agent_run by naming them explicitly. An agent can identify the tool's purpose without inspecting other definitions.

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?

It provides explicit eligibility criteria ('Only a paused or requires_approval run can be cancelled'), lists the exact error codes for invalid states and missing IDs, and names the alternatives ('Use resume_agent_run or approve_agent_run'). This is textbook usage guidance with no ambiguity.

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