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

Annotations already declare this a read-only, idempotent, non-destructive call, so the description is free to spend its words on non-obvious behavior — pagination contract (`cursor` = previous `next_cursor` while `has_more`), library scope beyond what the API can create, and the trap that `frames_review` reports `status: "processing"` while actually waiting on the user. That status-vocabulary warning is behavior an agent cannot get from annotations or schema.

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-loaded with the list semantics and pagination, then WHEN, then the story-episode guidance — a sensible priority order. The `story_stage` enumeration is long and slightly overlaps the schema's `kind` description, but each stage gloss carries real disambiguation value for an agent deciding whether to wait or render.

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?

With no output schema, the description compensates by describing row fields (`kind`, `story_stage`, `status`, `next_cursor`) and their meaning. For a three-optional-parameter list tool with full annotation coverage, an agent has everything needed to page correctly and route the result to the story tools.

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 100%, so the baseline is 3, and the description earns an increment by explaining why `kind` matters (story tools need the episode id) and how to read `story_stage` on returned rows, plus the fallback when `story_stage` is omitted. It adds little on `limit`, but the enum's downstream consequence is well covered.

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 opening clause gives a specific resource and ordering ('The account's videos, newest first') and immediately bounds scope ('the whole library, including videos made in the web app and with products this API cannot create'). It is clearly distinguishable from get_video (single item), list_uploads (raw uploads) and the story generation tools.

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?

An explicit WHEN clause names both triggering situations (user asks what they made; need a video from an earlier session), and it names the routing rule to siblings: 'THIS IS HOW YOU FIND A STORY EPISODE, and every story tool needs its id', with get_video indicated for the underlying job. When-to-use, why-to-use and alternatives are all present.

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