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

Annotations already declare readOnlyHint and openWorldHint, and the description adds substantial value on top: it asserts 'Does NOT bill anything' and warns that final billing depends on actual matched results and account plan, plus it discloses the response content (min/max cost, billable unit, free quota impact, approval recommendation). This is exactly the kind of non-obvious behavior an agent needs.

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?

Four sentences, each carrying distinct information: purpose, when to use, what is returned, and the billing caveat. The core purpose is front-loaded and there is no filler.

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?

With no output schema, the description usefully enumerates the return fields and the non-binding nature of the estimate, so an agent can interpret results. The remaining gap is the entirely undocumented input parameters, which an agent must infer from names alone.

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 0% across 3 parameters. The description never explains what 'operation', 'estimated_records', or 'countries' mean, nor why the operation enum or country codes matter for the estimate. With zero schema-level documentation, the burden falls on the description and it does not compensate.

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 (estimate) and resource (billable units and rate-limit impact for a planned FirmaDB job), and explicitly frames it as a pre-execution dry run. This is clearly distinguishable from siblings like firmadb_enrich_companies, which actually perform work.

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?

Gives an explicit trigger: 'Use this before batch enrichment or any agent workflow where the user might be charged for many results.' It does not name the sibling tools it should precede (e.g. firmadb_enrich_companies) directly, but the when-to-use condition is unambiguous.

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