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

Annotations already declare readOnlyHint=true and destructiveHint=false, but the description adds real behavioral context beyond them: the preview consumes no credit, the projection is a CEILING rather than a guarantee, and company matching on website may shift the count. It does not, however, describe pagination, latency, or error behavior. Strong added value over the annotation baseline.

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 cost framing, then enumerates the reported fields. Mostly earns its length, though the aside 'there is no reason not to look first' is slightly rhetorical filler and the companies_to_create_at_most caveat is dense. Not wasteful enough to drop below 4 given the density of useful detail.

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 must carry the return-value burden and does so thoroughly: match count against the cap, a ten-person sample with name/title/company, existing-account count, companies to be created, email coverage, and projected spend. Combined with the credit and ceiling caveats, an agent has everything needed to interpret and act on the result.

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% with only two parameters, both already documented in the schema ('Create it first', 'Call list_crm_connections first'). The description reinforces the run_id/connection_id prerequisites but adds no syntax or format detail beyond what the schema provides, so the baseline 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?

States a specific verb and resource ('preview_records_run' → who a created CREATE run would add and its cost) and immediately distinguishes it from its closest sibling by framing it as the pre-flight check for dispatch_run. It is clearly separate from preview_enrichment_run and preview_normalize_scheme by naming the exact artifact (a CREATE run) it previews.

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?

Explicit when-to-use guidance: 'Call this before dispatch_run every time,' justified by the cost asymmetry (searching is free, only creating is charged). It also states an exclusion/limitation ('It cannot tell you which people are already contacts in the CRM'), so the agent knows what this preview cannot answer.

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