cancel_render_job

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

Adds substantial context beyond the annotations: it discloses the underlying executor mechanism (UMoviePipelinePIEExecutor / CancelAllJobs), the honest headless behavior, and the fact that cancellation stops the executor's whole render rather than a single named job. Annotations cover safety flags but not this operational nuance.

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?

Front-loads the action, then the caveat, then the return shape in a compact form. The parenthetical '(honest headless gate)' is a slightly informal touch, but the structure is otherwise tight and each sentence contributes.

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?

No output schema exists, yet the description supplies the return shape ({canceled, was_rendering, note}), the failure mode, and the headless expectation. Combined with the annotations, an agent has everything needed to invoke and interpret the result.

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 100%, so the single job_name parameter is already documented in the schema. The description adds no further parameter semantics, which matches the baseline of 3 when the schema carries the load.

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 ('Cancels the in-progress movie render') and immediately scopes the condition ('if one is running'). An agent can distinguish this from siblings like create_render_job, delete_render_job, and render_sequence_to_movie without opening any 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?

Clearly explains the operating context: renders run inside a Play-In-Editor session, so a headless editor normally has no active executor and reporting was_rendering:false is expected, not an error. It does not explicitly name alternative tools, but the when-to-use and when-nothing-happens conditions are spelled out.

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