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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds genuine value beyond that: results are ordered newest first, the full status lifecycle is enumerated, and paused campaigns explain why they stopped. It does not cover pagination behavior or what happens when limit truncates results.

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 key facts are front-loaded (what it returns, newest first), but the middle is a long undifferentiated run-on field inventory, and the embedded Ukrainian example queries are useful routing signal yet add bulk. It is informative rather than tight.

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 correctly carries the return-value burden by enumerating every metric an agent would need (sent, delivered, opened, clicked, bounced, complaints, unsubscribed, orders, revenue). The only gap is that the secondary output — segments and letter templates — is mentioned without any indication of its shape.

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 0%, so the description must carry parameter meaning and it only partially does. It explains 'campaign' (id or name) and its enumerated status list implicitly documents the 'status' filter values, but 'limit' is never mentioned and neither is the interaction between status filtering and result ordering.

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 names the resource precisely (e-mail campaigns/newsletters with their results) and enumerates the exact fields returned, so an agent knows this is a read of campaign performance data, not a draft-creation tool. It stops short of explicitly contrasting itself with siblings like email_marketing_campaign_draft, though 'sending is only in the cabinet' implies the boundary.

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?

It gives concrete selection guidance: omit 'campaign' to list everything, pass 'campaign' (id or name) to get one, and it names the user questions this answers (how the send went, how many opened, which campaigns exist). It also rules out the send action entirely, but never names an alternative tool for drafting or contacts.

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