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

Annotations already declare readOnlyHint=true, so the description does not need to emphasize safety. It adds context about retrieving monthly spend, but does not disclose any additional behavioral traits like response format or rate limits.

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, concise sentence that front-loads the main action ('Check your automatic credit top-up configuration') and then adds the spend detail. No unnecessary 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?

Given no parameters and an output schema existing, the description is adequate. It tells the agent exactly what information is returned. A perfect score would require mentioning that it is read-only, but annotations already cover that.

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?

With no parameters, the schema coverage is 100%. The description adds meaning by explaining what the tool retrieves, which is the top-up configuration and spend. Baseline for 0 parameters is 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 uses the verb 'check' and specifies the resource 'automatic credit top-up configuration' along with 'this month's spend'. This clearly distinguishes it from sibling tools like 'configure_auto_top_up' and 'disable_auto_top_up', which are write operations.

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 tool is for viewing current settings and usage. It does not explicitly state when to use it versus alternatives, but the read-only nature is evident from the name and annotations, providing clear context with no exclusions.

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