Credit consumption history

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

Beyond the readOnlyHint annotation, the description adds behavioral details: newest-first ordering, inclusion of diagram and surface, and the session-scoped running tally. It also states 'Free (read-only)', reinforcing safety without contradicting annotations.

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 three sentences with no filler. It front-loads the primary function, provides a direct use case, and adds a key additional detail about the session tally, all in a compact structure.

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?

The description covers the main purpose, returned fields (credit, diagram, surface, session tally), and ordering. With no output schema, it compensates well, though it could mention pagination or the specific return shape. The schema covers parameters, so the description is sufficiently complete for 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% with descriptions for all 7 parameters. The description adds context for action, source, and diagram_id by mentioning task types and surfaces, but doesn't explain limit, since, until, or cursor beyond the schema. This meets the baseline for high schema coverage.

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: 'List how much credit each past task charged' with ordering, diagram, and surface details. It distinguishes itself from siblings like get_usage by emphasizing per-task history, not total usage.

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 gives a concrete use case: 'Use this to answer "how much did each task cost?"' and mentions the session tally. However, it doesn't explicitly mention when not to use it or direct users to alternative tools such as get_usage for overall consumption.

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