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

Annotations already declare readOnlyHint=true, destructiveHint=false and closed-world scope, so safety is covered. The description adds real behavioral context beyond that: that reading must precede editing, that editing avoids regenerating existing assets, and that editorUrl is a link to hand to the user. It omits auth requirements and any note on how editRevision should be used, which keeps it below a 5.

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 tight sentences with no filler: what it returns first, then when to call it, then why it beats the alternative. Return contents are front-loaded and the routing advice follows, so the agent can act after one pass.

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 an output schema present, the description does not need to explain return shape, and annotations carry the safety profile — so coverage of the essentials is good. The only gap is that editRevision's role (presumably a handle for edit_project) is never connected to a sibling, leaving a small inference for the agent.

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 100% and both parameters are documented in-schema, including the intended use of "at" to locate the item behind a moment. The description adds no parameter-level meaning, so the baseline 3 applies.

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 and resource ("Read what is on a project's timeline") and enumerates the returned fields — item id, type, track, timing, text/caption styling, motion graphic props, editRevision, editorUrl. That is enough to distinguish it from siblings like view_frames or get_project_status without opening any 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?

Gives an explicit sequencing rule ("Call this first when changing an existing video") and names the alternative it beats (render_video), including the condition that selects it: the video is mostly right. The implied exclusion — don't re-render when only edits are needed — is stated rather than left to inference.

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