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

With no annotations, the description carries the burden. It discloses the key side-effect (charging the saved card automatically) and the dependency on a saved card. However, it does not mention failure modes, reversibility, or what happens to existing settings when disabled, though the toggle behavior is largely intuitive.

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 two sentences, front-loaded with the main action, and every sentence adds essential information (behavior and prerequisite). No wasted words.

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 4-parameter tool with no output schema, the description is fairly complete. It covers purpose, triggering condition, and prerequisite. It does not describe the response format, but that is not necessary given no output schema, and the overall usage context is adequately covered.

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%, so baseline is 3. The description adds value by explaining the behavioral context of threshold and recharge amount (e.g., 'balance below the threshold'), which helps the agent understand how the parameters interact, earning a 4.

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 enables or disables automatic wallet top-ups, using a specific verb and resource. It distinguishes itself from sibling tools by describing the auto-recharge mechanism and prerequisite (saved card), making it unambiguous.

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?

Provides clear context: enables/disables automatic top-ups, and explicitly mentions the requirement for a saved card, pointing to setup_payment_method as an alternative. Does not explicitly state when not to use it, but the usage context is well implied.

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