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

Annotations declare non-read-only, non-idempotent, non-destructive, closed-world, but do not cover the key lifecycle. The description adds genuinely new behavior: you receive your own bound key on their account, shown once (a secret that cannot be re-read), which is important for correct handling. It stops short of noting failure modes for invalid/expired codes.

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?

Three short sentences, front-loaded with the core action, then the provenance of the code, then the required activation step. No filler.

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?

An output schema exists so return values need no explanation, and the description still covers the key state, the no-key precondition, and the required follow-up call. Nothing essential for correct invocation is missing.

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 both parameters are already documented in the schema ('the bj-… code from bus_invite', 'your name inside the team'), which is effectively what the description echoes. Baseline 3 is appropriate; no syntax or format detail is added 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?

States a specific verb (join) and resource (existing team via invite code), and explicitly contrasts with the sibling that creates the code (bus_invite). An agent can distinguish this from bus_mint/bus_signup without opening a 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?

Specifies the precondition (a teammate made the code with bus_invite), the condition (join an EXISTING team, no key needed), and the follow-up action (bus_configure with harness and accept_from). This is full when/when-not/next-step guidance.

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