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

With no annotations, the description carries the behavioral disclosure burden. It does add useful context: pricing date, per-runner rates, allowance handling, and an extra before/after price-cut report. However, it does not spell out assumptions or limitations, such as how plan allowances are applied or that this is a rough estimate rather than an actual invoice.

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 clauses deliver the core purpose, pricing basis, allowances, and an extra output with no wasted words. The most decision-relevant information is front-loaded, and every sentence earns its place.

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?

For a calculation tool with a fully documented schema, the description is nearly complete: it states the rates, the allowance behavior, and the historical comparison output. It lacks only a brief statement of assumptions or edge cases, which would make it fully self-sufficient given no output schema.

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 description coverage is 100%, so the structured schema already documents every parameter. The description adds value by supplying the exact current rates per runner type, but it does not deepen meaning around plan, publicRepo, or how the minutes combine. Baseline 3 is appropriate.

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 verb and resource ('Estimate a GitHub Actions monthly bill') and immediately narrows scope with exact runner rates, plan allowances, and the pre-cut comparison. This clearly distinguishes it from sibling calculate_* tools by domain, so an agent can select it without inspecting other definitions.

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 clear contextual guidance: it is for estimating GitHub Actions spend with January 2026 rates and plan allowances, and it advertises a historical comparison. It does not explicitly list alternatives or when not to use it, but the domain-specific framing makes the intended use unmistakable.

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