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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds only that the default response is a 'short summary' and the underlying endpoint; it says nothing about pagination behavior or result ordering beyond what the schema states.

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?

Two compact sentences with the core purpose front-loaded, followed by the optional-detail hint. The trailing 'GET /api/labels' is mild implementation trivia but takes little space.

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 simple, non-destructive, two-optional-parameter list tool with full schema coverage and clear annotations, the description supplies everything needed to select and call it; no output schema means return-value explanation is not required.

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 100%, so both parameters are already documented, and the baseline is 3. The description adds marginal value by explaining that passing `fields` yields more than the default short summary, but the `limit` parameter and the field-name pattern are left entirely to the schema.

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?

States a specific verb and resource ('List the labels that can be put on events') and adds concrete examples (Confirmed, Urgent). It does not explicitly distinguish itself from the sibling scheduleit_list_label_groups, so a reader must infer that this returns labels rather than label groupings.

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?

Usage is implied by the phrase 'labels that can be put on events,' suggesting it is a lookup performed before tagging events. No explicit when-not or named alternative (e.g. list_label_groups) is given, leaving the agent to infer the choice between the two.

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