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

Annotations already declare readOnly/idempotent/non-destructive, and the description still adds substantial non-schema behavior: APIFY_TOKEN requirement, per-company-row billing, robots.txt compliance and reads from the investor's own site, error-with-run-ID on failure, and free summary rows that explain empty sources. That is exactly the operational context the annotations cannot convey.

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?

Front-loaded with purpose and input forms, then output shape, then constraints. Dense but every element is load-bearing; the parenthetical list of eleven investor names is mildly redundant with the schema's enum-like list of the same names.

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 14 parameters and no output schema, the description does the necessary work of describing return rows and the summary row, plus failure behavior. Remaining gaps are minor — nothing about ordering, deduplication across sources, or how only_new/state_key interact with free vs billed rows.

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%, so every parameter already carries its own description with defaults and limits. The description's mention of YC filterability by batch, industry, region, status, and search words merely restates what the schema documents, adding no syntax or interaction detail beyond it.

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 ('Build a list of the companies a venture capital firm or accelerator backs') and immediately names the two accepted input forms and the shape of the output. An agent knows exactly what this tool produces without opening the 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?

Clear about what to supply (investor/accelerator names or portfolio page URLs) and about the YC-specific filtering path, plus the default of Y Combinator when nothing is given. There are no sibling tools to compare against, so no exclusions are needed — but it also doesn't explain when this tool is the wrong choice (e.g. non-VC company lists).

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