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

Goes well past readOnlyHint=true: it discloses the 60/hour quota, the stateless server model and the history passback protocol, the two possible modes (write_script vs answer), and the full return envelope. The "web server keeps nothing" line resolves any tension between "writes a script" and readOnlyHint, since nothing is persisted.

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 free quota and the one-turn-at-a-time model, then uses clean Args/Returns sections. A few range restatements (1-4000 chars, 15-240) duplicate the schema, which is the only real waste in an otherwise tight definition.

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, and the description compensates by spelling out the return keys (ok, mode, reply, script, target_seconds, chips, history) and what to do next. For a 6-parameter, nested-object, multi-turn tool, nothing an agent needs to call 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?

Schema coverage is only 33%, so the description must carry the load, and it does — all six parameters are explained with intent, not just type: `length` only when the user named a target, `script` for editing an existing draft, `source` from read_article. The "pass `history` from the last answer" instruction is operational meaning the schema cannot express.

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 pair and resource — "Writes or improves a Video Studio script with the user, one turn at a time" — and names the follow-on sibling (studio_create_project) so the agent can place it in a workflow. The multi-turn, conversational nature is explicit, which no sibling name alone would convey.

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?

Gives concrete operating context: it is free at 60 calls/hour, it is stateless so `history` must be passed back each turn, and the script it returns is meant to feed studio_create_project. It lacks explicit exclusions (e.g., when to use ai_short_draft or ai_short_revise instead), so it stops short of full alternative routing.

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