Create Source

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

With annotations already indicating destructive behavior (destructiveHint=true) and external world interaction (openWorldHint=true), the description adds the key behavioral detail that the tool 'returns a redirect checkout URL', which is especially valuable because there is no output schema. It also clarifies the specific e-wallet types. This goes beyond the annotations and helps the agent anticipate the result.

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 a single, front-loaded sentence. It states the core action first and adds the return behavior in parentheses. No wasted words 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 tool with 5 parameters and no output schema, the description covers the essential context: purpose, specific payment types, and the return value (redirect checkout URL). The schema already documents parameters fully, so the description is sufficient for basic selection and invocation. It could mention prerequisites or side effects, but the annotation hints and return description cover most needs.

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 provides 100% description coverage for all parameters, including amount units and type enum values. The description adds minimal extra parameter meaning—only naming the e-wallet types (GCash/GrabPay) already present in the schema. It does not exceed the baseline set by the rich schema.

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 specific verb and resource: 'Create a GCash/GrabPay payment source'. It also differentiates from sibling tools like create_payment_intent or create_checkout by naming the specific payment source type and the return value (a redirect checkout URL). This leaves no ambiguity about what the tool does.

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 implies the usage context: you need a GCash/GrabPay payment source with a redirect checkout URL. However, it does not explicitly state when to use this tool over alternatives such as create_payment_intent or create_checkout, nor does it provide exclusion criteria. This is implied usage rather than explicit guidance.

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