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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds genuine non-structured context: the accepted domain input formats, that it returns the full profile, and that a free StartupHub.ai account is required (an auth prerequisite).

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 short sentences, front-loaded with the core action, followed by input formats, return shape, the alternative tool, and the account requirement. No sentence is redundant with another.

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 read tool with no output schema, the description covers action, input flexibility, result nature ('full profile'), auth requirement and sibling routing. Return-value detail is thin, but with no output schema and readOnly annotations the description is essentially complete.

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 0% and the schema only declares domain as a bare string, so the description carries the burden. It does so usefully by enumerating accepted formats (raw URL with path, stripped 'example.com', with or without paths), which is meaning the schema does not convey.

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 ('Look up a single startup by its website domain') and scopes it to a single result. It explicitly distinguishes itself from the batch sibling match_companies_by_domain, so an agent can route without opening either 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?

Names the alternative tool and the condition that selects it ('Use match_companies_by_domain instead for batches of 2+ domains'), which is clear routing guidance. It does not, however, distinguish this from other single-entity siblings such as get_startup or search_startups, so full when/when-not coverage is absent.

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