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

Annotations declare readOnlyHint=false and destructiveHint=false, so the mutation/safety profile is already covered. The description adds that the input must be a prior generation id and that instructions are free-form text, but says nothing about whether the edit is synchronous or returns a job (the presence of check_job among siblings makes this a real ambiguity).

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?

A single front-loaded sentence with zero filler; the verb, resource, identifier format, and instruction mechanism are all stated before the reader stops.

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 mutating 6-parameter tool with no output schema, the description covers the core contract but omits the result shape (does it return an image, a job id?) and the async/await behavior implied by check_job. Annotations carry the safety profile, but the workflow gap leaves the agent inferring too much.

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 67% and the schema itself documents overlay, resolution, aspect_ratio and model in detail. The description only restates the two required parameters (image id and instruction), adding no format, constraint, or interaction detail beyond what the schema already provides. 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 (edit) and resource (a previously generated image), plus the required identifier format (img_… id) and the natural-language instruction mechanism. It implicitly separates itself from generate_image by requiring a prior generation, but never names or contrasts with a sibling explicitly.

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 only implied: the agent can infer this is for modifying an existing image rather than creating one. There is no explicit when-to-use/when-not, no prerequisite statement (e.g., the source id must come from generate_image), and no guidance about the relationship to check_job.

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