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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety and open-world scope are covered. The description adds genuinely useful non-annotation context: a fixed cost of 3 credits charged only on success. It doesn't discuss rate limits, failure modes, or caching, but the cost/billing disclosure is meaningful added value over the structured fields.

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?

Three front-loaded sentences: purpose, usage/exclusions, then cost. Every sentence carries information the agent needs, and nothing is repeated from the schema or annotations.

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?

There is no output schema, and the description compensates by enumerating the return contents (name, description, industry, size, founding year, HQ, employees, revenue, funding, social links, technologies, logo, brand colors). Combined with usage boundaries and cost, an agent has everything needed to decide and invoke correctly.

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 coverage is 100% with only two parameters, both already described ('Company domain.', 'Optional name hint.'). The description's 'by domain' reinforces that domain is the lookup key but adds no format, normalization, or hint-behavior detail beyond the schema, so the baseline 3 applies.

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?

Opens with a specific verb+resource and scope: 'Enrich company data by domain.' It then enumerates the returned fields, making the tool's offering concrete. It also explicitly names what it is not (site-intel for technical domain facts, profiles for people), so an agent can separate it from siblings without opening schemas.

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?

'Use for business facts about a company' gives the affirmative trigger, and the two exclusion clauses route the agent to site-intel for WHOIS/DNS/SSL/hosting and profiles for a person. This is explicit when-to-use plus named alternatives — the top of the scale.

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