Partial-update an appointment

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

With no annotations, the description carries the full burden and delivers: it reveals the fetch-and-merge behavior, the effect of passing `end` (re-spans, multi-day vs collapse), `start` alone (moves and keeps length), and the error condition for bare dates on timed events. This is far beyond what the schema provides and leaves no hidden behavioral surprises.

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 long but every clause earns its place, explaining intricate edge-case behavior that would otherwise be inscrutable. It front-loads the core purpose and merge semantics before detailing parameter interactions; slightly verbose, but appropriately so for a 10-parameter tool with no annotations.

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 parameter-rich mutation tool with no annotations or output schema, the description covers the essential invocation logic: how to switch timed/all-day, how start/end interact, and one explicit error condition. It stops short of describing return values or other error cases, but nothing an agent needs to call it correctly is missing.

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 0%, so the description must compensate; it does for the high-risk parameters (`start`, `end`, `all_day`) with concrete scenario rules, and even explains `year`/`month` as the locating page for the fetch. The simple string fields (`subject`, `location`, `notes`, `attendees`) and `appointment_id` are left to schema-name inference, but the semantics of 'only fields you pass are altered' covers them adequately.

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 and resource ('Partial-update an appointment') and immediately distinguishes it from the Cozi PUT full-replace semantics. Among siblings like create_appointment and delete_appointment, the 'partial-update' wording makes the tool's role unambiguous.

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 provides conditional usage guidance ('To switch a timed appointment to all-day pass all_day=true; to switch to timed pass new start/end') and explains the merge model, which clarifies when this tool is appropriate for modifying an existing appointment. It doesn't explicitly name alternatives or exclusions, so it stops short of a 5, but the context clearly separates it from create/delete siblings.

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