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

Annotations provide only generic safety hints (readOnlyHint=false, destructiveHint=false); the description adds critical non-obvious behavior: the request covers all dates, produces an undoUrl for withdrawal, and the status URL alone cannot withdraw it. It does not contradict the annotations, and this is substantive context beyond structured fields.

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 purpose and precondition are front-loaded, and the undoUrl instruction is important. However, the second sentence partly repeats the purpose ('It asks to join the activity') before adding the all-dates scope, and the undoUrl guidance spans two sentences that could be tightened.

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?

The description supplies the consent precondition, scope, and undo mechanism needed to invoke this mutating tool correctly. It leaves some context implicit—such as the pending-request/approval lifecycle and exact response shape—but with no output schema and full parameter coverage, it is largely complete.

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 the schema already documents spaceId, activityId, and name. The description adds no parameter-level syntax or meaning beyond 'for your person,' so the baseline of 3 is appropriate.

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 uses a specific verb and resource ('ask to join an activity') and clarifies scope ('all its dates, not one evening'). It does not name or differentiate this tool from siblings such as activities_add or other join-related tools, so it stops short of 5.

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 gives an explicit precondition: 'only after they said they want to.' That is clear context for when to use it, but it names no alternative tools or when-not-to-use cases, matching a 4 rather than a 5.

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