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

With no annotations provided, the description carries the full burden and does so thoroughly. It discloses outbound network calls, read-only nature, file write side effects (including permissions 0600), idempotency, error handling on CLI crash, and the behavior around missing credentials. This is far beyond typical transparency.

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 long but well-structured with clear paragraphs and a logical flow. Every sentence provides meaningful information, though a few phrases like 'it answers exactly that comparison in one shot' add little and could be trimmed. The length is justified for the tool's complexity, but it isn't maximally concise.

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?

Given the tool's complexity, the description covers all essential context: prerequisites, side effects, parameter details, error behavior, return value structure, and explicit usage constraints. An output schema exists, but the description still explains return keys, which is helpful for an agent understanding the data shape without relying solely on the 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?

The input schema only has 'args' as an array of strings with no description, so schema coverage is 0%. The description fully compensates by explaining the exact expected argv format, required flags, optional flags, automatic --json appending, --help usage, and three real examples. This is exemplary parameter documentation.

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 opens with a precise, specific verb and resource: 'Compare AI-coding-tool spend between a "before" and "after" date window across two tools.' It clearly distinguishes itself from other tools by explicitly listing what it does not handle ('general usage analytics, per-line-item billing detail, or tools other than cursor, claude-code, claude-code-personal, copilot, opencode, codex').

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 provides explicit when-to-use guidance with concrete example user queries, and also gives an explicit when-not-to-use list. It even states the exclusions in detail, making the decision boundary extremely clear.

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