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

Annotations already declare readOnlyHint, openWorldHint=false and destructiveHint=false, so safety is covered. The description adds genuinely useful behavioral context beyond that: no paging, all events returned in one response, upcoming/past split by date, newest-created-first ordering, and differing field payloads per list. That said, some of the per-item field detail overlaps with the separate output schema, so it falls just short of a 5.

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, front-loaded with the use case before the return-shape detail and the sibling routing. It is dense rather than padded, though the enumeration of returned fields is heavier than strictly needed given an output schema exists.

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 zero-parameter list tool with an output schema, an agent has everything it needs: when to call it, what it returns at a high level, how the results are partitioned and ordered, and which tool to use instead for detail or guest data.

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?

The tool takes zero parameters and schema coverage is 100%, so the baseline is 4. There is no parameter semantics to add and the description correctly avoids inventing any.

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+resource (list the account's invitations) and immediately distinguishes itself from siblings by naming lemonvite_get_invitation and lemonvite_list_guests as the tools for detail and guest data. An agent can tell exactly which tool to pick without opening a schema.

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 opens with an explicit trigger ('when the user wants to find or pick one of their invitations, or when you need the event_id') and closes with clear routing rules to the two alternatives, each with its own condition. This is explicit when/when-not/alternatives guidance.

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