buy_credits

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

With no annotations, the description must carry the full disclosure burden. It clearly discloses the key behavioral traits: returns a checkout URL (not a direct purchase), requires human involvement to complete payment in a browser, and automatically credits the agent afterward. This goes beyond schema and gives critical context for an agent deciding whether to call the tool.

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 sentences with the purpose front-loaded and the behavioral flow explained in the second sentence. No redundancy, minimal words, and every sentence 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?

For a tool with no output schema, the description adequately explains what is returned (a URL) and the subsequent flow (human payment, automatic crediting). Minor details like error handling or exact URL format are omitted, but nothing an agent needs to invoke the tool correctly is missing.

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%: both 'key' and 'pack' have descriptive text, including the enum values with prices (starter: 500cr/$5, pro: 2500cr/$20). The description adds no parameter-level semantics beyond what the schema already provides, 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 states a specific verb and resource: 'Get a Stripe checkout URL to buy credit packs.' It clearly distinguishes this from sibling tools like purchase_skill by specifying the resource is credits, not a skill. This is a specific, non-tautological purpose statement.

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 usage (buy credit packs) but does not explicitly mention alternatives or exclusions. Sibling tools like purchase_skill exist, but the description doesn't state when to use buy_credits over purchase_skill beyond the resource type. This is adequate but lacks explicit guidance.

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