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

Goes well beyond the annotations by disclosing a hard failure mode (combining entity_id with an image reference returns HTTP 500) and the deliberate design decision to always generate from the reference image alone. It does not cover cost/credit consumption or rate-limit behaviour for a non-idempotent generation call, so it stops short of full coverage.

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-loads the core purpose and uses bullets and headers so a reader can scan it. It is long, and the aside about entity_id being 'deliberate, not a workaround to fix later' is close to editorial padding, but for a 7-parameter tool with mutual-exclusion rules the length is largely earned.

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 complex generation tool with no output schema, it covers purpose, when-to-use, mutual exclusivity of the reference inputs and project routing. It omits any description of the generated output or the meaning of model/aspect/include_preview, which leaves minor gaps an agent must resolve by inference.

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?

With schema coverage at 0%, the description carries the parameter burden and does so for the four critical params: it distinguishes character vs photo_media_id as mutually exclusive, explains the lookup source for character, and describes prompt's expected content and project_id's effect. The model, aspect and include_preview params remain unexplained in both schema and description, leaving a gap.

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 with precise scope: 'Generate a NEW image of the SAME PERSON/character as an existing photo or portrait.' It explicitly separates itself from generate_image, generate_character_image and generate_scene by claiming to be 'the ONLY tool for generate another picture of <character I already made>'.

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 a concrete when-to-use scenario ('here is my photo, now put me in a suit / in a park') and an explicit routing rule: pass exactly one of character or photo_media_id, with each branch explained and tied to a setup path (create_character_from_description, create_character_from_photo, list_characters). It even states when NOT to use entity_id/character_slot_index and why.

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