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

readOnlyHint only tells the agent this is a safe read; the description goes well beyond that by decoding lifecycle edge cases — `done: true` with still-failed items, `retry_count` meaning an automatic second attempt, and `fallback_from` meaning a provider swap after a content-policy rejection. This is behavior an agent could not infer from annotations.

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?

Purpose is front-loaded, followed by the return shape, the polling rule, and then field semantics — a logical order with no filler. Every clause (done semantics, retry_count, fallback_from) carries distinct 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?

There is no output schema, so the description takes on the return-value burden and does so thoroughly: it enumerates the JSON keys, explains `done`, and interprets the per-item fields. Nothing needed to call or interpret this tool 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?

Single parameter with 100% schema description coverage, including the vb_<hex> format, so the schema already carries the burden. The description implies batch_id filtering but adds no syntax beyond what the schema states, making the baseline 3 correct.

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?

Names a specific verb+resource ('aggregated progress of a video batch') and ties it to its producer (lab_animate_batch), while explicitly distinguishing it from lab_job_status. An agent can tell exactly what this returns without opening a 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?

'poll this ONCE per batch instead of calling lab_job_status per clip' gives an explicit alternative plus the condition that selects this tool over it. It also states the prerequisite (a batch started by lab_animate_batch).

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