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

Beyond the annotations, the description discloses critical behavior: the balance changes only after verified test payment, not after opening the checkout link, and that idempotency_key should be reused for retries. It also clarifies this is test-only and no real money is accepted, which is exactly the context an agent needs for a mutation/write operation.

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 description is two dense sentences with no wasted text. It front-loads the purpose and then immediately adds the key behavioral caveats about payment verification and retries.

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 two-parameter funding tool with no output schema, the description covers the purpose, amount units, idempotency behavior, and payment verification caveat. It does not describe what the returned checkout session contains or any endpoint/auth prerequisites beyond the authenticated machine context, but an agent can invoke it correctly.

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 0%, so the description must carry parameter meaning. It explains amount_cents is integer EUR cents with 100 = EUR 1.00, and it explains idempotency_key should be reused for retries. The idempotency_key format or max length is not described, but the core semantics are covered.

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 states a specific verb and resource: create or retrieve an offline-sandbox Stripe TEST Checkout session for funding this machine's test wallet. It clearly distinguishes the operation from sibling tools like get_wallet or create_checkout by naming the exact session type and test-wallet funding scope.

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?

The description clearly establishes when to use it: to fund the authenticated machine's test wallet via a test Checkout session. It also explains retry behavior with idempotency_key and that no real money is accepted, though it does not explicitly name alternatives or when not to use this tool.

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