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

Discloses behavior well beyond the annotations: the secret is shown only one time, the key owns its own creator id with no identity attached, and creation is rate-limited to 3 keys per network per day. The non-idempotent annotation is corroborated by 'call this once' and the one-time secret display, with no contradiction.

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?

The core action and the one-time secret warning are front-loaded, and each clause carries real information (auth header usage, free-stamp check, rate limit, human redirect). It is dense but long for a single-parameter tool, with the rate-limit and redirect details slightly crowding the primary instruction.

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 compensates by naming the two return fields that matter (secret and freeStamp) and how to act on each. Auth requirements, free-tier limits, and the fallback payment path are all covered, leaving nothing an agent needs missing before calling.

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?

Only one optional parameter, and schema coverage is 100%, so the schema already documents `label` as a recognizable name. The description adds useful semantics about result fields (secret, freeStamp) but nothing extra about the label itself beyond what the schema states.

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 ('Provision a persistent API key') and immediately scopes it as agent-self-service with no human, browser, or email. It also enumerates the sibling tools the resulting key unlocks, so an agent can place it correctly relative to buy_stamps, create_proof, and the rest without opening another 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?

Explicitly says 'Call this once' and to store the returned secret, and it gives concrete branching advice: check freeStamp, and if false use buy_stamps or x402 before the first stamp. It also redirects the out-of-scope case (3 free stamps a month or a human-owned account) to makemark.io/account, which is an explicit when-not rule.

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