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

Annotations already declare destructiveHint=true, idempotentHint=true and openWorldHint=true, and the description adds a genuine security constraint about never reusing secrets. However, it does not say what the destructive behavior means in practice — whether existing keys are overwritten, whether prior credentials are invalidated, or what permissions are required.

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 short sentences, front-loaded with the action and scope, followed by the one non-obvious behavioral constraint. No filler or redundancy.

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 destructive, open-world mutation with a free-form nested object parameter and no output schema, the description covers the security rule but leaves the overwrite semantics and any result/confirmation behavior unexplained. It is adequate but not complete for a write tool of this risk profile.

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% and the schema itself documents both fields, including the example shape of the nested key object and the note that credentialId comes from list_connections. The description adds no parameter-level meaning beyond that, so the baseline of 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 uses a specific verb+resource ("Save the API keys of a payment app") and enumerates supported providers (PayPal, Alby, BTCPay Server, HitPay), so an agent can tell this apart from read-side siblings like list_api_keys or get_app. It stops short of explicitly naming an alternative tool, which keeps it from a 5.

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?

It gives a procedural rule ("Ask the user to type the keys themselves; never reuse other secrets") but never states when to use this versus other credential/connection tools, nor any prerequisite such as first obtaining the credentialId via list_connections. Usage is implied rather than scoped.

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