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

Annotations already declare readOnlyHint=true, so the description doesn't need to restate safety. It adds behavioral context by clarifying the operation is scoped to one event and by characterizing the tool as cheaper/more precise than `whoami`, which helps the agent reason about cost and precision.

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 two focused sentences with no filler. The core purpose is front-loaded, and the usage comparison is packed into the second sentence without redundancy.

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 read-only tool with one parameter and no output schema, the description covers purpose, scope, and when to choose it over the main alternative. It doesn't enumerate possible return roles in detail, but 'organise, judge or only take part' gives enough context for an agent to call it correctly.

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 only parameter `event_slug` has a minimal schema description ('Slug of the event.'), and the tool description adds that it identifies 'one specific event.' This is adequate baseline coverage but does not meaningfully extend beyond 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?

The description clearly states a specific verb and resource: 'roles the signed-in user holds at one specific event.' It explicitly differentiates itself from the sibling `whoami` by being 'cheaper and more precise' for this narrower use case, so an agent can distinguish it from related tools.

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?

The description gives explicit when-to-use guidance: use it when the event is already known and the goal is to check whether the user can 'organise, judge or only take part.' It also names `whoami` as the alternative, telling the agent when not to use this tool.

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