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

Annotations already cover the read-only safety profile, so the bar is lower, yet the description adds substantial non-obvious semantics: person-booked rows and closed months are excluded from the agreement rate, and differently-booked rows name the claiming rule. It doesn't disclose auth/permission requirements, but the counting logic is genuinely useful behavioral context beyond the 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?

Purpose is front-loaded in the first sentence, followed by return content and exclusion rules. It is slightly dense with several clauses, but every sentence carries meaningful information about behavior or output composition.

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 single-parameter read-only tool with an output schema and full annotations, the description covers the essential non-obvious behavior (what is excluded and why) sufficiently. Nothing an agent needs to call it correctly is missing.

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% and there is only one parameter (companyId), which the schema fully documents. The description adds no additional parameter meaning, so the baseline of 3 for a fully-covered schema 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?

States a specific verb and resource: comparing the categorization rule engine against a company's current books, explicitly in a non-mutating "shadow" mode. This is clearly distinguishable from live-write siblings like transaction_categorize_transaction and from preview siblings like transaction_preview_categorization_rule.

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 (evaluate the engine against books before committing) but never made explicit, and no alternative sibling is named. The distinction from the live engine is hinted at via "the live engine would not touch them," but there is no stated when-to-use/when-not-to-use guidance.

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