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

Annotations already declare idempotentHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds the ownership requirement and the CONFLICT-on-mismatch behavior, which is genuinely useful. It omits a key behavioral trait for a mutation with almost all-optional parameters: whether omitted fields are left untouched or cleared, and what happens when the caller does not own the character.

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?

A single front-loaded sentence with no filler; the parenthetical is earned because it flags the concurrency guard. It is efficient but so terse that it leaves the update semantics unstated.

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 7-parameter mutation with 29% schema coverage and no output schema, the description needed to cover partial-update semantics, the undocumented editable fields, and success/failure shape. It covers only the ownership constraint and the conflict case, leaving the bulk of what an agent needs underspecified.

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 only 29%: five of the six optional fields (name, color_tag, description, prompt_suffix, reference_image_key) carry no schema description, and the description does not explain any of them or their length constraints/format. The one parameter it touches, expected_updated_at, is already documented in the schema, so the description adds essentially nothing here.

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 names a specific verb (Update) and resource (studio_character) and adds an ownership scope, which distinguishes it from studio_character_read/create/delete by name alone. It stops short of explicitly naming the sibling that selects a different path, so a 4 rather than a 5.

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?

'a studio_character you own' implies a prerequisite (ownership) and the compare-and-set note hints at the concurrency case. However, there is no explicit statement of when to use this versus studio_character_create or the read/list variants, and no guidance on when the expected_updated_at guard should be supplied.

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