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

Beyond the annotations, the description discloses a rate limit (5 links/hour), link validity (24 hours), credit arrival timing (within seconds), and cost (free). These are critical behavioral details that help an agent anticipate the tool's consequences. The description aligns with the annotations (readOnlyHint=false, openWorldHint=true) and adds practical constraints.

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 concise and front-loaded, opening with the primary action. Each sentence provides distinct value: purpose, use case, behavior (credits and validity), rate limit, and pack reference. There is no filler or redundancy that undermines clarity.

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 single-parameter tool with a fully covered schema and useful annotations, this description is sufficiently complete. It explains what the tool creates, when to use it, rate limit, validity, timing of credits, and cost. The return value (a link) is implied and no output schema exists, so no further detail is necessary.

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 already fully covers the only parameter packId with an enum and a description pointing to get_credit_balance/docs. The description only repeats the 'see docs' guidance and does not add new meaning or syntax beyond the schema. With 100% schema coverage, the baseline of 3 is appropriate.

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 with a specific verb and resource: 'Creates a Stripe Checkout link for a credit pack.' It also differentiates from sibling tools by tying the action to a concrete scenario (balance running out mid-task) and the benefit of providing a one-click payment link instead of manual instructions.

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 explicitly identifies when to use this tool: 'when the balance runs out mid-task.' It also suggests an alternative to using the tool (giving instructions), offering practical guidance. However, it doesn't explicitly name sibling tools for comparing balance or exclude other scenarios, so it doesn't fully earn a 5.

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