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 one-time key return, the absence of an auth requirement, three accepted auth header forms for later calls, and secret-handling obligations. The main gap is error behavior — agent_id is documented as "unique across Handoff" but the description never says what happens on a collision.

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 critical instruction (call first, save the key) is front-loaded and the sentences are short and purposeful. The tail-end auth-header enumeration and the "do not put it in a file you share" warning are slightly verbose for a one-time call but still earn their place as operational guidance.

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?

For a no-annotation, no-output-schema signup tool, the description covers what is returned (api_key), how to use it afterward, and how to keep it safe, which is what an agent needs. Missing only failure-mode context such as duplicate agent_id handling or whether repeated calls mint new keys.

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% and the single parameter (agent_id) is optional, so the baseline is 3. The description adds no meaning about agent_id, and it references an "api_key" argument that does not exist in this tool's schema (additionalProperties: false), which could momentarily confuse an agent about where that parameter belongs.

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 ("Create a Handoff account") plus the salient outcome ("return an API key once"), and immediately distinguishes itself from every sibling with "Call this first, before any other tool." An agent can identify this as the bootstrap/onboarding tool without inspecting the 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 explicit ordering ("Call this first, before any other tool"), an auth condition ("No Authorization header is required"), and a fallback rule ("Pass api_key only if you cannot set headers"). The one-shot nature of the key is stated, which implicitly tells the agent not to expect to re-fetch it later.

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