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

Annotations only declare readOnlyHint and openWorldHint; the description adds the material behavioral facts an agent needs — $0.25 USDC per hot company via x402 on Base, a 4-company / $1 cap per paid call, no charge when zero companies are hot, 15-minute quote expiry, and 3 free scans per day per IP. None of this is recoverable 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 purpose is front-loaded in the first clause and the rest is a dense but ordered walkthrough of the paid flow. For a two-phase payment tool every sentence carries operational weight, though the run-on structure with inline pricing and caps makes it slightly harder to scan than it could be.

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?

An output schema exists, so return shapes need not be re-explained, yet the description still surfaces the key return behaviors (cold domains come back with intent_score, hot domains yield a company profile, overflow lands in more_hot). Combined with the payment, quota, and expiry rules, nothing an agent needs to invoke this correctly is missing.

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 67%, so the description must compensate and largely does: it explains the two mutually exclusive modes (domains alone vs quote_id alone), states the min_intent_score default of 70, and clarifies that quote_id is the artifact from step 1. It stops short of explaining the domain format constraints (no scheme/path/port, 253-char limit) beyond what the schema already says.

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 opening sentence states a specific verb and resource: 'Buying intent for a list of companies: find which of 2 to 25 domains are hiring hardest.' It scopes the input size (2-25 domains) and the outcome (hiring intent), which clearly separates it from siblings like get_company_hiring_intent or batch_lookup without needing their schemas.

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 gives an explicit two-step protocol: Step 1 is free (send domains, optional min_intent_score), Step 2 requires quote_id plus payment. That is clear when-to-use guidance for each mode. It does not, however, compare itself to any named sibling tool, so the agent still has to infer when find_hot_buyers beats get_company_hiring_intent.

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