set_character_portrait

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

No annotations are provided, but the description discloses that the operation overwrites an existing portrait (destructive), is free (no generation runs), and that the portrait serves as the starting frame for talking animations. It doesn't mention error cases or permissions, but for a mutation tool, key side effects are addressed.

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 sentences, front-loaded with purpose, includes alternative tool reference. Every sentence adds value; nothing extraneous.

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?

Given the schema is fully documented (100% coverage) and this is a simple attach operation, the description covers the key context: free operation, overwrite behavior, downstream use in vocal_animation, and the alternative generation tool. Lacks only minor details like response type or error handling, but acceptable for this tool's simplicity.

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% (both character_id and image are fully described). The description adds no parameter-specific details beyond the schema, but it explains the tool's purpose and relationship to vocal_animation, which helps context. Baseline 3 is appropriate since schema already handles parameter semantics.

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?

Description clearly states the tool attaches a bust portrait to a saved character, with specific verb ('attach') and resource ('saved character'), and distinguishes it from portrait_character_pro by noting this is free with no generation runs. The sibling tool is explicitly named with direction parameter.

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?

Description explains when to use it: attaching a portrait directly without generation. It also directs users to portrait_character_pro when they need to generate from a full-body sprite, giving an explicit alternative. It doesn't explicitly state when NOT to use it, but the contrast with the sibling covers the main ambiguity.

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