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

With no annotations, the description carries the full burden. It discloses that the invite is single-use, returns specific artifacts (Telegram/WhatsApp deep links, QR code), and binds messenger identity. The warning that start_login does not open this tool is a useful behavioral caveat beyond the schema.

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 compact and structured in two clear paragraphs — one for functionality and one for access requirements. It avoids redundancy while including necessary context, though the access note could be folded in more tightly.

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 2-parameter tool with no output schema or annotations, this description covers the essentials: purpose, return artifacts, user behavior, and auth prerequisite. It omits edge cases (e.g., member already in circle, invite expiration), but these are not required for a call to succeed.

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%, and the parameter descriptions ('Circle ID', 'Member ID to invite') already convey the meaning. The description text does not add additional nuance about the parameters, so the baseline of 3 applies.

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 opens with a specific verb and resource: 'Mint a single-use enrollment invite for a Circle member.' It also explains the mechanism (deep links and QR code) and how the recipient uses it, which clearly distinguishes this from sibling tools like add_circle_member or add_circle_member_channel.

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 provides an explicit prerequisite ('needs a Proof account', 'Authenticate this client') and an exclusion ('start_login does NOT open this tool'). While it does not explicitly contrast with alternative invite/add tools, the enrollment-invite framing implies when it should be used, and the auth note gives concrete operational guidance.

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