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

Annotations already declare destructiveHint=true, so the agent knows this is a mutating operation. The description adds the meaningful constraint that only in-flight runs are cancellable, but is silent on irreversibility, permissions, or what state the run ends in; the API-version note is endpoint trivia rather than behavioral context.

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 purpose is front-loaded in one tight sentence, but the second sentence about v2 vs v1 and the raw 'Trigger.dev: POST /api/v2/runs/{runId}/cancel' string adds little for an agent choosing a tool and reads as internal documentation spillover.

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 one-parameter mutation tool with destructiveHint annotated and no output schema, the description supplies the essential purpose and the in-flight scope. It is nearly complete; a sentence on the resulting run state or required permissions would close the remaining gap.

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?

There is a single required parameter with 100% schema description coverage ('The run to cancel.'), so the schema already carries parameter meaning. The description only echoes runId inside the raw path template, adding no semantics beyond the schema. Baseline 3 applies.

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 an in-flight run') and scopes it to in-flight runs, which no sibling tool does (the closest siblings, replay_run and reschedule_run, do something different). An agent can identify the tool's job without opening the 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?

The 'in-flight' qualifier implies the tool applies only to currently executing runs, which is a useful usage boundary, but the description never explicitly states when to reach for this versus replay_run or reschedule_run, nor any prerequisite such as run state. Usage is implied rather than specified.

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