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

Annotations already declare readOnlyHint and idempotentHint, so safety is covered; the description adds genuinely new behavior beyond that—the return shape (action plus summary or usage fields) and the pagination rule 'increment page only while hasMore'. It stops short of disclosing auth/permission requirements or rate limits, but the pagination and return contract are meaningful additions.

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?

Three dense sentences with zero filler: purpose and scope first, then return/pagination contract, then alternative routing. Front-loaded and every clause carries information an agent needs.

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?

No output schema exists, yet the description enumerates the return fields (items, page, pageSize, total, hasMore) and the iteration rule. All six parameters are schema-documented, and the alternatives are named, leaving nothing critical missing for correct invocation.

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 the baseline is 3; the description nevertheless adds semantics the schema lacks—the conditional pagination rule tied to hasMore and the notion of a default/permitted action value. This goes slightly past restating schema fields.

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 (read) and resource (personal balance/access or paginated billing) and immediately scopes it with 'not spending authorization', which separates it from the financially-adjacent sibling spending_policy. An agent can identify the tool's function without opening the schema.

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?

Explicitly routes the agent: 'Use spending_policy for automatic-spending limits and list_models for model prices,' and clarifies the tool is not for spending authorization. It also notes the action defaults to 'the permitted action', covering the no-arg case.

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