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

Adds non-obvious behavior beyond the annotations: a 12/day per-workspace cap and a 24h dedup window where a repeated call will not resend unless a fresh `resend` value is passed. The annotations only supply coarse flags (readOnly=false, destructive=true, idempotent=false); the description explains the actual dedup semantics that nuance that flag. It does not say what the call returns or whether it affects campaign analytics.

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?

Three dense sentences, front-loaded with what the tool does before the identifier sourcing and the rate-limit/dedup caveats. Every sentence earns its place and nothing is repeated.

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 7-parameter, 4-required mutation tool with no output schema, the description covers the operational risks (rate limit, dedup, forced resend), which is the main thing an agent needs. Minor gap: it never clarifies whether a test send consumes production quota or pollutes campaign statistics, and the destructiveHint=true annotation is left unexplained.

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%, and the schema already documents variantId provenance, resend ('never sent to the API'), personalization enum behavior, and leadId. The description largely restates the variantId/accountId sourcing already present in the schema, adding no new syntax or format detail. Baseline 3 is correct when the schema carries the weight.

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 (send one rendered preview of a sequence step variant) plus the exact scope: single address, chosen mailbox, rendered as a lead would see it. An agent can immediately distinguish this from campaign-sending tools like start_campaign or from get_campaign, which merely supplies the variant id.

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?

Gives concrete provenance guidance ('Take variantId from get_campaign', 'accountId from list_mailboxes') and the resend condition, which is genuinely actionable routing. It stops short of stating explicit exclusions (e.g. 'do not use for real sends' or how it differs from actually launching the campaign), so it is clear context without formal when-not guidance.

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