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

Annotations already indicate destructiveHint=true, idempotentHint=true, and readOnlyHint=false, so the safe-vs-destructive profile is covered. The description adds meaningful behavioral details beyond annotations: partial updates, empty-string clearing, all-day event handling via omitted start_time, and local-time semantics.

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 four short sentences with no filler. Every sentence carries load-bearing guidance: what changes, when it is allowed, time semantics, and patch/clear behavior. The most important scoping statement is front-loaded.

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 10-parameter mutation tool, the description and schema together cover purpose, field semantics, partial update behavior, and clearing side effects. A minor gap is the absence of any statement about return values or success/failure behavior, since there is no output schema to fill that in.

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 70%, so the schema does most parameter documentation. The description adds useful semantics: 'omit start_time for an all-day event', 'Times are local (no time zone)', and the partial-update/clearing rule. This goes beyond the schema's raw patterns and names.

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 uses the specific verb 'Change' and identifies the resource: 'the shared event everyone sees on the RSVP page'. It enumerates the mutable fields (title, date/time, place, description), which makes the tool's purpose unambiguous and distinguishes it from sibling tools like set_rsvp or create_plan.

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 usage context: 'Only after the group agreed', and explains the modification strategy: 'Send only the fields to change; an empty string clears a field.' It does not explicitly name alternatives or state when not to use this tool, so it misses the top score.

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