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

Annotations only cover the basic safety profile, and the description adds substantial context the annotations cannot: the five-minute TTL, the required header name and target endpoint, the 2FA/unlocked/agents-allowed preconditions, and the consequence that a key without a second factor cannot withdraw at all. It leaves the response shape and re-mint behavior implied rather than stated.

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?

Two dense sentences, front-loaded with what the token is and where it goes. The URL restatement (api.taifoon.dev/vault/withdraw) is mildly redundant with the POST /vault/withdraw path and makes the second clause feel run-on.

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?

Despite having no parameters and no output schema, the description covers purpose, invocation, and eligibility gating, which is what an agent needs to call it correctly. It stops short of stating what the call returns (an opaque token string) or whether repeated calls mint separate tokens, though idempotentHint=false implies that.

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?

Zero parameters, so there is no parameter semantics to clarify; baseline 4 applies. The description appropriately spends its words on preconditions and embedding instructions instead of inventing parameter detail.

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 concrete artifact (a five-minute proof of second-factor passage), its scope (venue vault / withdrawal), and the exact verb-resource pairing. An agent can distinguish this from siblings like vault_prepare or my_vaults without opening any 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 invocation context (send as the x-step-up header of POST /vault/withdraw) plus the preconditions under which it can be minted: second factor configured, account unlocked, agents allowed. It does not name a sibling alternative or an explicit when-not path, so it falls short of a 5.

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