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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the ethical bar is lower. The description adds a genuinely useful non-schema fact: 'Uses LeadBoxer credits per call', which warns the agent this is a metered operation. It does not cover failure modes (unknown domain, insufficient credits), keeping it at 4.

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?

One tight paragraph: what it returns first, then use cases, then the credit cost last. Dense but every clause carries information. The parenthetical '(company lookup, firmographics)' is mildly redundant with the title.

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 one-parameter enrichment tool with no output schema, the description supplies the field list (so the return shape is known), the input format, usage contexts, and the credit cost. Only error/quota behavior is unaddressed.

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% and the single 'domain' parameter is documented with examples and format constraints in the schema itself. The description's 'stripe.com (no https:// or www)' merely repeats the schema's example and guidance, adding no new semantics — baseline 3.

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+resource ('Company enrichment by domain') and enumerates the returned fields (name, industry, employee range, HQ, phone, LinkedIn, specialties, aliases). Sibling tools lookup_email, lookup_ip and get_credit_balance are clearly different resources, so the agent can route without opening a schema.

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 concrete use cases: enriching sign-ups and CRM accounts, scoring ICP fit, and profiling a company from a work email's domain — the last implicitly routes between this and lookup_email. There is no explicit 'do not use when' or cost-alternative guidance, so it stops short of a 5.

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