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

Annotations only cover readOnly/openWorld/idempotent, so the description adds real value by disclosing the external side effect: exactly one email goes out containing a Confirm link and code, sign-in is free, and connect_verify blocks waiting for the click. It does not say what happens on resend/expiry or whether calling twice sends two emails, despite idempotentHint=false.

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-loads the action and the prerequisite in the first two clauses, then the call to action; almost no wasted words. The parenthetical '(shared 0.61.0)' is an opaque version tag that costs a clause without helping an agent decide or call.

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?

With no output schema, the description still conveys the essential return value by referencing connect_verify(request_id), so the agent knows a request_id comes back and what to do with it. Missing are error/expiry handling and whether re-invocation is safe, which matter given idempotentHint=false.

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% and the schema's own property descriptions already explain email, language tags with fallback to English, and that 'firm' is never worth asking for. The description restates email and language but adds nothing about the parameters beyond the schema, so the baseline 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?

States a specific action (sign in with the user's email), names the auth mechanism (no password, emailed Confirm link plus six-digit code), and explicitly separates itself from connect_verify by describing that tool as the follow-up step. An agent can tell it apart from whoami/describe/connect_verify 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 a concrete gating rule — 'Required for every tool except whoami and describe' — and names the required next call (connect_verify(request_id)) with the timing cue 'right away'. It stops short of saying what to do when the user is already signed in (e.g. check whoami first, do not re-call), which is the last piece needed for a 5.

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