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

Beyond the readOnly/idempotent annotations, it discloses cost and auth behavior ('requires an APIFY_TOKEN and consumes Apify credits per listing found'), the free path for unlisted companies ('come back free with row_status not_listed'), error handling semantics ('returned as an error with its run ID'), and the meaning of confidence scores. These are meaningful operational details an agent cannot infer from 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?

The description is a single dense paragraph but is front-loaded with the purpose, then the marketplaces, then the return shape, then cost/auth. Every clause carries information, though the long marketplace and field enumerations make it heavier than strictly necessary.

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 carries the return-value burden and does so well: per-row fields, status values, confidence tiers, and the not_listed case. Combined with the auth, pricing, and error disclosures, an agent has everything needed to call this 7-parameter tool 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 description coverage is 100%, so the schema already documents domains, skipCache, proxy_mode, company_name, marketplaces, company_domain, and max_charge_usd. The description reinforces the domain/name/domains relationship and the confidence implication of name-only matching, but adds little syntax or format 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?

States a specific verb and resource ('Find which app marketplaces list a company') and enumerates the ten marketplaces checked, so the agent knows exactly what data comes back. It also spells out the row shape (listing URL, name, installs, rating, review count, last update, status, match confidence), making the tool's output intent unmistakable.

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?

It clearly states the acceptable input modes ('Give a company domain, optionally its name, or a list of domains') and notes that omitting 'marketplaces' checks all ten, plus when to use skipCache. There are no sibling tools to disambiguate against, but it stops short of explicitly framing when this tool should not be used.

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