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

With no annotations, the description carries the burden of behavioral disclosure. It reveals that the endpoint is public and gated on code knowledge, which is a useful auth-related trait. It does not mention error cases or rate limits, but for a simple balance check, the key behavioral trait (no bearer required) is disclosed.

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 concise sentences front-load the primary purpose and then provide key auth context. Every word earns its place, and there is no fluff 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 simple one-parameter tool with no output schema, the description is complete. It explains what it does, the auth requirement, and implies the return value (remaining balance). The absence of an output schema is mitigated by the explicit statement of what is checked.

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 provides a 100% coverage description for the 'code' parameter ('Gift card code (full string as printed on the card).'). The tool description adds marginal value by mentioning 'using its code,' but this largely restates the schema. Baseline 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 function: 'Check a gift card's remaining balance using its code.' It uses a specific verb+resource (check balance, gift card, code) and distinguishes itself from sibling tools like get_cart or list_products, none of which deal with gift cards.

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: it is a public endpoint and no bearer token is required, gated on knowledge of the code. It does not explicitly mention alternatives or when-not to use it, but given the absence of related sibling tools, this is a minor gap and context is sufficient for an agent to select it appropriately.

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