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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so safety is covered. The description adds substantive context beyond this by stating what the report measures (capture rate, untracked spend, top diverging models). It does not mention the lookback window behavior, which would have earned a 5.

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?

A single dense sentence that front-loads the core comparison and then lists the metrics. No filler, no restatement of the title.

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?

An output schema exists, so return values need not be explained, and annotations cover the safety profile. However, the unexplained 'days' window and the absence of any sibling routing leave material gaps for a comparison tool surrounded by overlapping cost-reporting siblings.

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?

There is one parameter ('days') with 0% schema description coverage, so the description bears the burden of explaining it. The description never mentions a time window, default of 30, or the maximum of 90, leaving the agent to infer the period's effect on results from the schema alone.

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 names a specific resource ('tracked spend against what OpenAI and Anthropic billed') and enumerates the three outputs (capture rate, untracked spend, models that differ most), so the agent knows exactly what it returns. It does not, however, differentiate itself from close siblings like get_spend, get_customer_cost, or compare_models.

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?

There is no explicit guidance on when to choose this tool over get_spend, get_customer_cost, or compare_models, nor any stated prerequisites or exclusions. The outputs hint at a reconciliation use case, but the agent must infer that from the result list rather than from any routing statement.

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