Usero

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

Goes well beyond the annotations by disclosing the full state machine: pending until the user clicks, then a single ready payload with apiKey and setup, after which the pollToken is dead. That one-shot token lifecycle is exactly the kind of behavioral constraint annotations cannot express and prevents wasted retry loops.

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?

Every clause carries load: return shape, one-shot semantics, polling cadence, timeout, and post-ready actions. The most decision-relevant facts (poll cadence, one-time ready) are stated directly without preamble.

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, so the description carries the return-value burden and does so precisely, naming both status states and the fields inside the ready payload. Nothing needed to drive the polling loop or act on the result 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 coverage is 100% and the single pollToken is already documented as coming from start_signup, so the baseline is 3. The description adds real meaning on top by explaining the token's lifecycle (dead after a ready response), which tells the agent the token is not reusable.

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 (poll) tied to a named sibling (start_signup) and names the resource (signup status). An agent immediately understands this completes the flow begun by start_signup rather than being a standalone lookup.

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?

Explicitly says when to call it (after start_signup), how to call it (every 5 seconds for up to 15 minutes without ending the turn), and what to do next (apply the setup snippet, then call create_client for the product). This is a complete operating procedure, not just a hint.

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

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

Adds substantial behavior beyond the annotations: the email-plus-button handshake, the requirement that opening the page alone does nothing, the 'Yes, connect' step, that no key is shown in the browser, a rate limit of 5 per email per hour, and a 15-minute link expiry. These are exactly the operational constraints an agent needs and cannot infer from readOnlyHint/destructiveHint/openWorldHint.

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?

Dense but front-loaded around the core action, and every clause carries operational value (flow steps, userCode handling, rate limit, expiry). The mid-sentence flow narration makes it slightly run-on, but there is little throwaway text.

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 supplies what the tool returns (userCode, pollToken) and how those outputs are consumed downstream, plus timing and quota limits. Nothing an agent needs to invoke and follow through correctly 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 coverage is already 100%, so the baseline is 3; the description earns extra by stressing the non-obvious constraint 'Ask for the user's email, do not invent one' and by tying the returned value (userCode, pollToken) back to what the user must supply. It does not add format/syntax detail beyond the schema, so it is not a 5.

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+resource (start signup) and immediately differentiates from the sibling by naming check_signup and its role ('That lets check_signup return an API key for this MCP client'). An agent can tell the two apart without opening either 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 clear contextual guidance: ask for the email rather than inventing one, complete the browser flow, and hand the userCode back so check_signup can produce the key. It stops short of explicitly excluding cases (e.g., 'skip this if a key already exists'), so it is strong but not fully exhaustive on when-not-to-use.

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