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

Annotations already signal mutation and idempotency, and the description adds meaningful behavioral detail: replace sets exactly the listed days (implying removal of unlisted ones) and modifications require user confirmation. This goes beyond the structured annotation hints without contradicting them.

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 two compact sentences with no filler. The core action comes first, followed by the essential mode distinctions and the confirmation requirement—every sentence earns its place.

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 mutation tool with moderate complexity, the description covers the date format, allowed horizon, mode behavior, and confirmation prerequisite. It does not describe return values, but no output schema is present and the absence is not a blocking gap for invoking the tool 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?

With only 60% schema coverage, the description compensates by explaining the two underdocumented parameters: dates (format and allowed range) and mode (default and exact semantics). Participant id/token are already described in the schema, so the description need not repeat them.

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 states a precise operation—setting which days a person is free—and clearly identifies the resource (availability days). The mode semantics further clarify how the update is applied, and there is no ambiguity with sibling tools like set_rsvp or update_event.

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 gives clear context for use: availability can only be set for dates between today and two years ahead, and only with user confirmation. It also explains when to use replace versus add/remove, though it does not explicitly contrast the tool with sibling alternatives.

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