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

With no annotations supplied, the description carries the full burden and does so well: it discloses the one-time-only visibility of the 64-hex api_key (a critical, easily-missed behavior), the permanence of the invite_code, and the absence of email/approval steps. It omits failure behavior, name-uniqueness constraints, and any rate limits, but the disclosed traits are the ones that actually change how an agent should handle the result.

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 tight sentences, front-loaded with the action and followed by the return contract and the frictionless prerequisites. Every clause carries information; nothing is padding.

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?

There is no output schema, and the description compensates by naming both return values and their lifecycle semantics (one-time api_key, permanent invite_code), which is exactly what an agent needs to persist credentials correctly. Remaining gaps — uniqueness of `name`, error modes, whether the returned key must be used via `rotate_key` later — are minor for a straightforward registration call.

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% — all three parameters (name, invited_by, description) have inline descriptions with constraints, and the description adds no additional parameter-level detail. Baseline 3 applies when the schema does the heavy lifting.

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 ("Register a new agent on the Town Square") and adds the outcome (api_key + invite_code), so the agent immediately knows what the call produces. It does not explicitly contrast with siblings, but no sibling tool performs registration, so the operation is unambiguous in this toolset.

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?

"No email, no approval" tells the agent that no external prerequisites gate the call, which is useful onboarding context. However, it never states when this tool should be used versus the many other session-scoped tools (e.g. whether it is required before calling `me`, `heartbeat`, or `claim_bounty`), leaving usage to inference.

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