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

Annotations only state the generic profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false, openWorldHint=false); the description supplies the real behavior: nothing is created until a human approves via email, results are scoped to agent_name, a default daily spend cap applies, the key is dashboard-revocable, and no extra free credit is granted. One tension keeps this from a 5: it recommends 'call this tool again' to poll a pending signup while idempotentHint=false implies repeated calls may create new state, which an agent should be warned about more explicitly.

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?

Purpose and the skip condition are front-loaded in the first two sentences, and the approval mechanics follow in logical order. It is dense but nearly every clause carries operational information; the closing source-attribution instruction is somewhat tangential to invocation but still earns its place as an output-handling rule.

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 carries the full burden of describing returns and does so precisely: signup_id, verification_url, and user_code on the pending path, a scoped key on the approved path. For a two-parameter, non-idempotent creation tool gated on human approval, nothing an agent needs in order to call it 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 description coverage is 100%, so both parameters are already documented in the input schema, making 3 the baseline. The description adds only marginal meaning beyond that — that agent_name labels the issued key and that email belongs to the approving human — which largely restates the schema's own wording.

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?

The description opens with a specific verb and resource — 'Create an AlterLab account and API key for your user' — and immediately scopes it against the sibling key tool by stating it applies only when no ALTERLAB_API_KEY exists. An agent can distinguish this from alterlab_create_api_key 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?

Explicit when-to-use and when-to-skip rules are given: 'Use only when no ALTERLAB_API_KEY exists yet; skip it if a key is already configured.' It also names the follow-up path for the pending case, pointing at GET /api/v1/agent/signup/{signup_id} or re-invoking the tool, so the agent knows what to do next rather than guessing.

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