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

Beyond the annotations (destructive=false, openWorld=true), the description discloses what the call returns (a link and short code), expiry behavior (link and login_id expire after 10 minutes), the required follow-up polling of login_status, and the credential prerequisites (access to the user's own account). That is exactly the behavioral context an agent needs before invoking.

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-loaded with purpose and return value, then the procedure, then the exclusion, then the triggers. The middle narrative about signing in 'for the user' is lengthy, but each clause maps to a real branch of the flow rather than 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?

No output schema exists, and the description compensates fully by describing the return payload (link + code, login_id) and how to retrieve the actual API key via login_status. It also covers the failure/fallback path and expiry, so an agent can execute the whole flow without further guidance.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The description instead documents the implicit inputs (user's browser/browser session) that drive the outcome.

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 ('Sign in to Hey Anon (or create an account)') plus the mechanism ('through Privy in the browser') and the no-API-key constraint. Readily distinguishable from the login_status sibling, which it explicitly names as the follow-up step.

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 explicit triggers (right after installation, tools failing with 'API key not set', user wants to connect) and an explicit exclusion with an alternative ('Not for OAuth connections (ChatGPT apps, Claude connectors)... the user connects with the client's own Connect button'). It even prescribes the degree of autonomy ('go through the whole flow yourself without asking the user to confirm each step').

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