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

The description discloses that the tool returns an error, that it was withdrawn in version 0.5.3, and that withdrawal is pending review of source terms. This adds meaningful behavioral context beyond the readOnlyHint annotation, which only indicates that no mutation occurs.

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The description is a single, front-loaded sentence that conveys the withdrawn state, the reason, the behavior, and the client-facing rationale with no wasted words. It is an exemplary concise definition for a stub tool.

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For a withdrawn tool with no output schema and a single legacy parameter, the description is largely complete: it tells the agent that calling it will error and why it exists. It stops short of specifying the exact error message or response shape, but that is minor for a deprecation stub.

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 schema already describes the url parameter as 'Previously a ycombinator.com/companies URL.' The description adds no additional parameter semantics, so the baseline of 3 is appropriate.

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?

The description clearly states that the tool now returns an error and is kept for existing clients, which communicates its current purpose as a deprecation stub. It does not explicitly describe what extract_yc originally did beyond implying it was a ycombinator.com/companies URL extractor, but the behavior is clear enough to prevent misuse.

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?

The description implies usage is limited to existing clients seeking a clear error, but it does not explicitly say 'do not use for new calls' or name any alternative tool. Sibling tools like extract_company_landscape might be relevant substitutes, but no routing guidance is provided.

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