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

The annotations already declare destructiveHint=true and readOnlyHint=false, and the description reinforces that with concrete detail: the supplied text REPLACES existing content, so the event should be read first, and omitted fields are left untouched. That is meaningful operational context beyond the annotations, though it says nothing about permissions or the dry-run path beyond what the schema already documents.

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?

Three tight sentences, front-loaded with the verb and scope, then the required input provenance, then the replacement hazard. Every clause carries distinct information and nothing is repeated.

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 six-parameter destructive mutation with no output schema, the description covers the critical unknowns: where eventId comes from, how text replacement behaves, and what is out of scope. The only shortfall is that it does not state what the tool returns or how dry_run behaves, but the schema partially covers the latter.

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 100% schema coverage the baseline is 3, and the description earns more by explaining the replacement-not-patch semantics, the omit-to-preserve rule, and the source of eventId. It still leaves dry_run, person, and project semantics entirely to the schema, which is acceptable given the coverage.

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 specific verb ('Rewrite the words on') and a bounded resource (title, description, or both) on an event the member already has, which separates it from a general event mutation. It does not name the sibling that handles the excluded fields (date, price, capacity, publishing), so an agent must infer that another tool covers them.

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?

It gives clear when-to-use context: wording only, get eventId from list_my_events, read the event first, and send full replacement text rather than a patch. It also carves out a negative scope by forbidding date/price/capacity/publishing changes, though it does not point to the tool that should handle those instead.

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