Request a free API key

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

With no annotations, the description carries the full burden and does well: it discloses the 100 calls/day rate limit, the data freshness limitation (up to yesterday), free-tier currency coverage, that the key is both returned and emailed with an example, and that it is sent via the X-API-Key header on this server and the REST API. It does not cover key expiry, revocation, or duplicate-email behavior.

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?

A single dense sentence that is front-loaded with the core action and then layers on tier limits, delivery mechanics, and header usage. It is efficient, though the second half could be split for readability.

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?

Given the presence of an output schema, the description need not explain return values, and it correctly focuses on tier limits, data freshness, key delivery, and how to use the key. Missing only edge-case behavior such as duplicate requests or key expiration.

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% for the single email parameter, so the schema already documents it thoroughly. The description only restates that the key is issued 'for an email address,' adding no extra syntax or format constraints beyond what the schema provides.

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 (issue) and resource (free EMpulse API key) with the required input (email address). This is clearly distinguishable from all sibling tools, which are data-retrieval endpoints, not key provisioning.

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?

Explains the offer in practical terms: free currencies, data up to yesterday, 100 calls per day, key returned and emailed. It does not explicitly say when not to use it (e.g., if the user already has a key) or mention alternatives, but the context is clear enough for an agent to act.

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