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

With no annotations, the description carries the full burden and does well: it discloses the semantic meaning of each state, that 'unreconciled' means no provider anchor has been compared yet, and a real coverage limitation (OpenRouter accounting covers only calls via the connected key). It stops short of stating read-only nature or any permission/prerequisite, which is a modest gap for a zero-param tool.

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?

Two dense sentences, front-loaded with the core purpose and followed by qualifiers. Every clause carries information, though the term 'Argus's itemized total' introduces project-specific jargon without explanation.

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 or annotations exist, so the description must explain return semantics and it does: states, drift %, and the meaning/limits of 'unreconciled'. It doesn't enumerate return fields (e.g., drift field name, provider list) or explain 'Argus', so it is strong but not fully self-contained.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The mention of spend_basis qualifying mtdSpendUsd refers to output fields rather than inputs, so it doesn't add parameter meaning.

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?

Opens with a specific verb+resource pair ('Cost-accuracy state per provider') and enumerates the three possible states (exact, estimated, unreconciled) plus the drift metric. This distinguishes it from get_request_costs or get_overview, though it never explicitly names those siblings as alternatives.

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?

Usage is implied rather than stated: the agent can infer it should call this when it needs to know whether spend numbers are trustworthy. The 'unreconciled' definition and the caveat about OpenRouter covering only calls through the connected key are useful qualifiers, but there is no explicit when-to-use/when-not or named alternative.

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