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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and a closed world, so the safety profile is covered. The description adds genuinely new behavioral context: the result is ordered newest-edit-first, and projects only exist after a timeline is opened. It does not say how many items come back or how the limit behaves, which is the remaining gap.

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?

Three front-loaded sentences: resource plus ordering, then a definition, then the usage rule with examples. Every sentence carries distinct information and the quoted user phrasings make the trigger condition concrete rather than vague.

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 read-only list tool with no output schema and full annotation coverage, the definition supplies what an agent needs to select it and reason about its results. The only shortfall is that the limit parameter and result-set size/pagination are left entirely to the schema, which documents nothing.

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 0% and the sole parameter (limit, 1-20) is never mentioned in the description, so the description does not compensate for the coverage gap. However, with only one self-explanatory bounded integer, the practical cost of that omission is small.

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?

The description states a specific resource ('the account's timeline projects') and an ordering ('newest edit first'), then defines what a project is ('a finished cut opened as an editable multi-track timeline'). It also distinguishes itself from assemble_video, edit_asset and pipeline runs, which produce videos that have no project until open_run_in_timeline is used.

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?

It gives an explicit when-to-use rule with concrete user phrasings ('the narration runs long', 'drop the music a bit') and an explicit when-not-to: use it to change a video rather than make a new one. It also names the sibling that creates the precondition (open_run_in_timeline), so the agent knows the routing path.

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