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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered and the description needn't restate it. What it does add is that the check covers two payment rails (Bitcoin, PayPal), implying async settlement, but it says nothing about what a call actually surfaces (paid/pending/expired) or whether repeated polling is expected.

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 front-loaded sentence with no filler, which is appropriate for a narrow read-only check. It is arguably too terse given the unexplained 'id' parameter, but the sentence itself earns its place.

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?

There is no output schema, so the description carries the burden of explaining what the check returns — and it doesn't. For a tool whose entire value is telling the agent whether a payment settled, leaving the possible result states (and what to do when still unpaid) unstated is a significant gap.

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 only 50%: api_key is documented in the schema but the required 'id' parameter has no description anywhere, and the tool description never explains that it is the top-up identifier. An agent must guess whether 'id' is the top-up id, an invoice id, or a request id — a real ambiguity in a codebase full of id-bearing siblings.

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 ('Re-check') and resource (whether a Bitcoin or PayPal top-up was paid), so the agent knows this is a payment-status read rather than an initiation. The 'Re-check' framing hints at a counterpart to top_up, but it never names that sibling, so differentiation is implied rather than explicit.

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?

'Re-check' implies this is called after a top-up has already been started, but there is no statement of when to call it (after top_up? while pending? on a poll interval?) and no explicit pointer to top_up as the initiating alternative. Usage must be inferred from a single word.

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