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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=true, and destructiveHint=false, so the safety profile is fully covered by structured data. The description contributes the master-API-key auth requirement and a per-request price disclosure, which are real additions, but says nothing about pagination behavior, result caps, or ordering despite eight list/filter parameters.

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?

Two short sentences, front-loaded, with the auth constraint stated immediately. The injected pricing comment block is boilerplate rather than substance, but it is clearly delimited and does not obscure the core purpose.

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 values need not be described, and annotations carry the safety profile. Still, for an eight-filter search over a domain-specific resource, the description omits what the results represent, default paging behavior, and how to choose this tool over sibling campaign/message endpoints.

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%, so all eight optional parameters (page, per_page, user_ids, emailer_campaign_ids, emailer_message_stats, not_emailer_campaign_ids, email_account_id_and_aliases, emailer_message_reply_classes) are already documented in the schema. The description adds no syntax, format, or combined-filter semantics beyond that, which is the expected baseline.

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 states a verb+resource ("Search for outreach emails"), but it largely restates the title and never clarifies what an "outreach email" is (emailer messages within a sequence) or how this differs from sibling search tools such as post_apollo_emailer_campaigns_search or get_apollo_emailer_messages_id_activities. Purpose is discernible but vague at the message-vs-campaign level.

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?

There is no when-to-use guidance, no when-not-to-use, and no mention of alternatives among the many sibling search tools. The only contextual note is an authentication prerequisite ("Requires a master API key"), which is useful but is not usage guidance.

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