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

With no annotations provided, the description fully carries the behavioral disclosure burden and excels. It discloses that the action replaces previous answers, that the server converts free ranges to slots, that an empty free array records an explicit 'can't make any' (shown as a ✗), and that withdraw:true removes the answer entirely. It also mentions the result reports unapplied ranges and reasons, which is far beyond the minimum.

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. The first sentence states the core action and side effect, the second clarifies important naming guidance and the server conversion, and the third distinguishes the two special cases plus the result reporting. It remains appropriately sized given the tool's complexity and is front-loaded with the most critical information.

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 the absence of an output schema, the description does enough to set expectations by mentioning that unapplied ranges are reported with reasons. It covers the two major edge cases (empty free and withdraw), clarifies the timezone-conversion behavior, and gives naming guidance. For a tool of this complexity, the description is complete and self-sufficient.

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?

The schema covers 75% of parameters with basic descriptions, but the description adds crucial semantics: 'name' should be the participant's human name for group recognition, 'free' as an empty array means an explicit 'can't make any', and 'withdraw' overrides the free array to remove the answer. These semantics are not expressed in the schema and materially improve invocation correctness.

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 opens with a specific verb+resource: 'Set a participant's free times on a plan', which clearly distinguishes this from siblings like whenna_get_plan or whenna_lock_time. It also immediately clarifies the key behavioral nuance that this replaces the participant's previous answer, making the tool's purpose unmistakable.

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 provides clear context for when to use the tool and even contrasts the two modes (empty free array vs withdraw:true), which steers the agent toward the correct usage. It doesn't explicitly name alternative sibling tools or say 'use when...', but the context is strong enough to differentiate it from the other tools. Lacking explicit exclusions prevents a 5.

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