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

Annotations already cover the safety profile (write, non-destructive, non-idempotent, closed-world). The description adds genuine context beyond them: no cost ('Free'), an explicit return value ('returns its id'), a consent prerequisite, and a post-condition ('A new presenter has no picture until its portrait is drawn there'). It does not restate the non-idempotent behavior, but the added disclosure is substantive.

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?

Three sentences, front-loaded with verb, resource and return value, then eligibility and the presenter/portrait caveat. Every sentence carries information, though the final sentence about the missing portrait is a slightly tangential detail that could be trimmed or merged.

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 16-parameter, nested-object write tool with no output schema, the description supplies what the schema cannot: cost, the returned id, eligibility limits, and the consent prerequisite. Combined with 94% schema coverage, an agent has everything needed to invoke it correctly.

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 description coverage is 94% and every parameter, including the nested palette, is already documented in-schema with per-kind applicability. The description only reinforces the presenter case ('described in words, not a real person'), adding little beyond what the schema says, so 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?

Opens with a precise verb+resource+outcome: 'Saves a brand kit, a product, a generated presenter or a stock voice to the library for reuse in ads, and returns its id.' The four kinds map exactly to the schema enum, so an agent can identify the tool and its scope without opening the schema, and it is clearly distinct from the make_* siblings.

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 an explicit eligibility rule with the reason: 'Only generated presenters ... and stock voices can be saved here: a real person's face or voice needs the consent the person records at https://ugc.fans/library.' This is a strong when/when-not statement, though it stops short of naming where the excluded case should go or naming any sibling alternative.

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