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

With no annotations provided, the description carries the full burden and does it well: it discloses that guest updates are sent unconditionally, that replacing attendees uninvites omitted people with cancellation emails, and that whole-series edits are unsupported. These are exactly the side effects an agent needs to anticipate.

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?

Four sentences, each earning its place: main action, partial-update instruction, guest notification warning, series limitation, and attendee replacement warning. There is no fluff or repetition of schema-provided details.

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 tool with no annotations and no output schema, the description covers the essential operational behavior: partial updates, guest emails, attendee replacement, and an explicit unsupported case. The remaining gaps are minor, such as how timeZone interacts with start/end and what the response contains.

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 only 22%, so the description must compensate. It maps most parameters to plain-language fields (title, times, description, location, guest list) and adds critical meaning around attendees replacement. It still leaves the timeZone parameter's role and any date-time format expectations to inference.

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 ('Change') and explicitly identifies the resource ('an event's title, times, description, location or guest list'). This makes the tool's scope obvious and distinguishes it from create/delete/list sibling tools without needing to inspect 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 clearly instructs to supply only fields being changed, which is the key partial-update usage rule. It also states when not to use the tool ('Editing a whole recurring series is not supported'), though it does not name an alternative sibling for series edits or for moves.

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