PostPaymentCollectionsIdPaymentSessions

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It mentions that the tool 'initialize and add a payment session,' implying a write operation, but doesn't specify permissions required, whether it's idempotent, error handling, or rate limits. For a mutation tool with zero annotation coverage, this is a significant gap, as it lacks details on critical behavioral traits beyond the basic action.

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 appropriately sized and front-loaded, with two sentences that efficiently convey the tool's purpose and usage context. Every sentence adds value without redundancy, making it easy to scan and understand quickly.

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?

Given the tool's complexity as a mutation operation with no annotations, 2 undocumented parameters, and no output schema, the description is incomplete. It explains the high-level action and context but lacks details on parameters, return values, error conditions, or prerequisites, which are essential for effective use in a checkout scenario.

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?

The input schema has 2 parameters (id and fields) with 0% description coverage, meaning the schema provides no semantic information. The description doesn't explain what these parameters represent, such as 'id' likely being the payment collection ID or 'fields' specifying payment session details. It fails to compensate for the low schema coverage, leaving parameters largely undocumented.

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 clearly states the tool's purpose: 'Initialize and add a payment session to a payment collection.' It specifies the verb ('initialize and add'), resource ('payment session'), and context ('to a payment collection'), making it easy to understand what the tool does. However, it doesn't explicitly distinguish this tool from sibling tools like 'PostPaymentCollections' or 'PostCartsIdComplete', which might also relate to payment or checkout processes, so it doesn't reach the highest score.

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 provides clear context on when to use this tool: 'during checkout, where you create a payment collection for the cart, then initialize a payment session for the payment provider that the customer chooses.' This gives a specific scenario and sequence of actions. However, it doesn't explicitly state when not to use it or name alternatives among sibling tools, such as other payment-related tools, so it's not a perfect 5.

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