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

Annotations already cover read-only, idempotent and non-destructive, so the bar is lower. The description still adds genuine value by disclosing the ACCOUNT_MISMATCH failure mode and its payload (both user ids), plus an explicit negative contract: no email, tokens, cookies or page content. It does not say what the success shape looks like beyond 'user id'.

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?

Four short sentences, front-loaded with the primary return value, then the error case, then the safety scope. Every sentence carries distinct information with no repetition of the annotations' wording.

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 and no parameters, the description must explain the return contract, and it largely does: a user id on success, an ACCOUNT_MISMATCH with both ids on divergence, and an explicit list of things never returned. The only gap is the concrete shape of the success response (field name/wrapping).

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?

Zero parameters, so the baseline of 4 applies. Nothing in the description is needed to explain inputs, and it does not waste space pretending otherwise.

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: returns the stable Browse Bridge user id for the signed-in account. Clear and concrete. It does not, however, distinguish this from the sibling browser_get_status, which an agent might reasonably confuse it with.

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?

Usage is only implied — the ACCOUNT_MISMATCH sentence hints at a diagnostic use case (verifying connector and extension are on the same account), but there is no explicit 'use this when...' or direction to/away from browser_get_status. Adequate but leaves routing to inference.

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