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

Annotations declare readOnlyHint=false, destructiveHint=false and openWorldHint=true, so safety direction is partly covered. The description goes further by disclosing genuinely non-obvious behavior: execution is asynchronous, the call returns a task_id and a credit cost, and the completed task's result carries the CDN URL. What it omits — failure handling, whether the credit is refunded on failure — is minor against that.

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?

Two sentences, zero filler. It front-loads what the tool does, then immediately answers the two things an agent most needs to know afterwards (async task, credit cost) plus where the artifact ends up. Nothing could be cut without losing 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?

For a 14-param async generation tool with no output schema, the description compensates well by describing the return shape (task_id, credit cost, CDN URL on completion). It is not fully complete: it never names composer_task_status as the polling counterpart, which is the natural next step an agent must take.

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 93%, so the schema already documents mode, seed idempotency, resolution cost tiers, path formats and frame fields in detail. The description adds only the 5-15 s duration bound, which is already encoded in the schema's min/max, so it does not meaningfully exceed the schema here.

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?

Specific verb + resource: 'Generates one Boreal-H3 clip (5-15 s) into the project as an async task.' The named artifact (a video clip of a bounded duration) naturally separates it from siblings like composer_generate_music or composer_voice_line. It stops short of 5 because it never explicitly contrasts itself with those siblings.

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?

Usage is implied rather than stated: the async framing and 'task_id' return signal that this is a long-running generation step whose output must be polled. There is no explicit when-to-use/when-not, no mention of composer_task_status for following up, and no prerequisite guidance beyond project_id being a required param.

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