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

Goes beyond the readOnlyHint=false annotation by disclosing the upsert side effect ('creates the entry as "completed" when it is not there yet') and the auth requirement ('Needs sign-in'). It stops short of saying whether an existing rating is overwritten, but this is a genuinely informative disclosure for a mutation tool.

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 tight clauses, front-loaded with the action and scale, then the side effect and auth note. No padding or redundancy.

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 three-parameter rating tool with no output schema, the description covers the action, scale, auth requirement, and the notable completion-creating side effect. The only real gap is behavior when a rating already exists.

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%, so all three parameters are already documented, including the enum for media_type and the numeric bounds. The description's '1 to 10 (decimals allowed)' largely restates the schema, so baseline 3 is appropriate.

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 (rate a title) plus the exact scale (1-10, decimals allowed) and the target scope (the signed-in person's library). This clearly separates it from siblings like write_review and add_to_library without opening any schema.

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?

Usage is implied by the verb and the mention of 'Needs sign-in' serves as a precondition, but it never states when to prefer this over add_to_library or write_review, nor any exclusions. Adequate but leaves routing to inference.

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