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

Annotations only say it is not read-only, is open-world and not destructive; the description adds the important behavior that this is a human-in-the-loop handoff producing an approve_url that must be delivered out-of-band, plus the follow-up polling call. It does not disclose link expiry, denial handling, or what happens if the human never opens it, so some operational behavior remains implicit.

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?

Three sentences, no filler, with the produced artifact (approve_url) and the follow-up call up front. The first sentence is a long colon-chained clause, and the usage triggers sit at the end rather than being front-loaded, which costs a bit of scannability.

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 four-parameter, zero-required, no-output-schema tool, the description covers the outcome artifact, the required human interaction, the sequencing to get_approval, and the precise error conditions that should route here. Nothing essential for correct invocation is missing, and return values are out of scope since no output schema exists.

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%, so the schema already explains number, reason, api_key and amount_cents, including formats and bounds. The description adds only marginal meaning — that the human sets the actual spending limit while amount_cents is the ask — and repeats the api_key-from-get_approval hint already in the schema. Baseline 3 applies.

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 names a concrete action and artifact: obtain an approve_url link that a human opens to sign in, fund, set a spending limit and approve. That is clearly distinct from siblings like get_approval (which it explicitly hands off to) and start_check. It stops short of naming the sibling set directly, so it is strong but not fully disambiguating on its own.

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 trigger conditions are given: 'Use this when a check is refused with free_check_used, insufficient_funds or key_limit.' The description also prescribes the sequence — show the link to the human, then call get_approval — so both when-to-use and what-to-do-next are unambiguous.

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