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

Annotations declare non-read-only, idempotent, non-destructive, and the description adds the crucial partial-update contract ('pass null for each field to keep'), which explains why the tool is idempotent and non-destructive. It does not say whether resizing a frame affects existing content or what is returned on success, but with annotations covering the safety profile this is solid.

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?

Two tight sentences, zero waste, with the update scope front-loaded and the null-keeps rule immediately after as the key operational fact.

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 six-parameter mutation tool with full schema coverage, complete annotations, and no output schema, the description supplies the essential partial-update semantics. It omits any mention of projectId's alternate targeting behavior and side effects of resizing, which the schema covers but the prose does not.

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 every parameter already documents its own null-keeps semantics and pixel units, so the description largely restates the schema. The 'null keeps it' rule is reiterated but no extra syntax, format, or interaction detail is added beyond what the schema provides.

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 (change) and resource (project) and enumerates the mutable fields: name, frame size, fps, background color. It is clearly distinguishable from create_project, delete_project, and open_project by the tool name and field list, though it never explicitly contrasts itself with siblings. Minor tension: it says 'the open project's' while the schema's projectId allows targeting a different project.

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?

Usage is implied by 'Change the open project's ... Pass null for each field to keep', which signals a partial-update tool, but there is no statement of when to prefer this over create_project, patch_film, or switch_branch. No prerequisites, no when-not conditions, no named alternatives.

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