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

Annotations only declare readOnlyHint=true, so the description carries most of the burden. It goes well beyond that: it explains the semantics of per-agent fields, the cross-agent user_aggregate caps, team-level ceilings, and threshold overrides. It also notes 'Only configured limits appear in the response,' clarifying absence behavior. This is rich behavioral context not derivable from annotations alone.

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?

Front-loaded with the core purpose, then systematically explains the response structure. It's information-dense without obvious filler, though the list of per-agent fields is slightly repetitive. Overall efficient and well-organized.

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 the tool has no input parameters and no output schema, the description must explain what the response contains and what it means. It does so thoroughly: it covers per-agent fields, cross-agent aggregates, team-level limits, threshold overrides, and the condition for their appearance. This is complete for an agent to interpret the output correctly.

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?

Zero parameters, so baseline is 4 per the rules. The description details the meaning of response fields and nested objects (user_aggregate, team), which compensates for the lack of an output schema and adds value beyond what the empty input schema provides. No penalty since there are no parameters to document.

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?

States a specific verb+resource: 'Get current spending vs. configured limits.' This clearly distinguishes it from siblings like request_purchase and retrieve_card, though it doesn't explicitly name those alternatives. The core purpose is 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?

Implied usage as a read-only informational tool, but no explicit when-to-use guidance or alternatives. An agent can infer it's for checking spending, but the description doesn't say e.g. 'use before request_purchase to verify capacity' or when not to use it.

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