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

Annotations already declare readOnlyHint=true, but the description adds genuinely new behavior: what it returns (reference image urls) and how the result is consumed downstream (image_refs / reference_image_urls for look consistency). It does not cover error behavior for an unmatched name, keeping it short of 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?

Front-loaded with the verb and scoped tightly to three sentences with no filler. The mid-sentence em-dash insertion of the listing rule is slightly awkward but the content all earns its place.

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 single-parameter read tool with readOnlyHint and no output schema, the description supplies the missing pieces: the return payload, the downstream parameter names it feeds, and the workflow ordering against regeneration. Nothing needed to invoke it correctly is absent.

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, but the description adds meaning beyond the schema: the examples ('use my character Dana') show what the name value looks like in practice, and the no-name case is framed as a listing operation rather than an error.

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 (fetch) and resource (saved character/product/style sheet), and enumerates the natural-language phrasings that map to it. The contrast with var2_save_character and var2_create_image is implicit but clear: this retrieves a saved sheet rather than generating one.

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 explicit routing rules: omit name to list saved sheets, and 'call this FIRST, never regenerate from a text prompt' for a referenced character. Both the when-to-use and the when-not-to-use (regeneration) cases are covered.

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