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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the description builds on that by adding the 'FREE' note, the nature of the returned data (portrait URL, consent flag, pose plates, voice), and that an empty list means genuinely no cast exists. It also reveals the indirect cost implication when reusing a creator vs generating a fresh one. That goes beyond annotations without contradicting them, though it stops short of detailing pagination or potential latency issues.

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?

The description is dense but every sentence earns its place. It starts with the core purpose, then details the output fields, then cross-references how to reuse the results, and finally gives explicit usage timing and fallback behavior. No filler, and the most important usage guidance is front-loaded. The length is justified by the complexity of downstream integrations.

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 there is no output schema, the description compensates by fully enumerating the returned fields (name, portrait URL, provenance, consent status, pose plates, voice) and how to interpret each. It explains the empty response case and exactly how to use the data with other tools. For a list tool, this is exceptionally complete — it even covers cost implications and continuity guidance, so an agent can act correctly on the results.

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% — the only parameter 'limit' is fully described ('max creators to return (default 24)'). The description does not add further detail about the parameter, which is acceptable given the schema already covers it. The baseline of 3 applies because the description adds no extra semantic value beyond the schema for this single parameter.

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?

The description states the specific verb 'list' and resource 'saved creators', defines what a creator is (on-camera cast, with examples), and explicitly differentiates from sibling tools by explaining how the output is consumed downstream (render_ad, generate_avatar, etc.). It is far more specific than just 'list creators' and leaves no ambiguity about what the tool returns.

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?

The description gives explicit when-to-use guidance ('CALL THIS BEFORE OFFERING TO GENERATE A NEW PERSON') and reasons (cost savings, continuity), and also explains the empty-answer case with an alternative path (offer generate_avatar/save_creator). It names specific alternative tools (save_creator, generate_avatar) and the condition for using them, leaving no inference needed.

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