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

Annotations only declare readOnly=false and destructive=false, which is weak coverage for a credit-spending tool. The description supplies the critical behavior: default is a dry run that spends nothing, the plan quotes an exact total, reactions must be passed back verbatim, and the total is never exceeded. That is exactly the context an agent needs to avoid an unintended spend.

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?

Front-loaded with what the tool produces and how many, then the required inputs, then the confirmation protocol. Dense and mostly waste-free, though the middle clause listing inputs restates the schema and could be trimmed.

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 9-parameter, credit-spending, two-phase tool, the description covers the input contract, the dry-run/confirm loop, cost bounds, and the 'grid card fills in as the clips render' progress signal. With an output schema present, return values need no further explanation.

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 100%, so the schema already explains image vs. character, the 2-10 count, mood/purpose overrides, and reaction keys. The description largely restates those fields ('Give a look id (image) or an influencer id') rather than adding format or constraint detail beyond the structured data.

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 with scope: 'Several clips of one influencer at once, each a different silent reaction from the library.' An agent can distinguish this batch operation from the singular create_clip / create_motion_clip siblings 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?

Spells out an explicit two-step protocol: call without confirm to get the plan and spend nothing, show it, then call again with confirm true and the same reactions. It also bounds cost ('never more than the quoted total'), but it never names a sibling alternative for single-clip or motion-clip requests.

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