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

Annotations already declare non-readOnly, non-idempotent, non-destructive, so the description is free to add the state model: the request stays pending and 'nothing can be sent until they say yes.' It also constrains the note to plain words with no links or email addresses, which is genuine behavioral guidance rather than annotation restatement.

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?

Front-loaded with the core action and the routing rule at the end where it belongs. Two adjacent sentences ('Nothing can be sent until they say yes. Only when your person asks.') restate the same pending-state idea, a minor redundancy in an otherwise tight definition.

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 mutation tool with no output schema, the description covers the pending-request lifecycle and the note format, which is most of what an agent needs. It stops short of describing duplicate-request behavior or the response, though idempotentHint=false already signals that repeat calls are not safely deduplicated.

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 coverage is 100%, so the baseline is 3, but the description adds real constraints beyond the schema's maxLength — the note must be plain prose describing who the requester is, with links and email addresses disallowed. That meaningfully narrows how the note parameter should be filled.

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+resource (send a friend request to someone on Oyeh), scoped by handle, and explicitly distinguishes itself from the sibling invite_friend. An agent can route correctly without opening any 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?

Gives an explicit alternative and the condition that selects it: 'If they aren't on Oyeh yet, use invite_friend instead.' It also states the prerequisite that the target already be a member, which is the key branch point against its siblings.

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