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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), and the description still adds genuinely new traits: newest-first ordering, the cursor-style paging contract, and the caveat that open counts are estimates because some inboxes open every email to scan. It omits the default page size and 10/30 limit bounds, which the schema already carries.

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 and ordering lead, followed by the caveats about status, paging, and the open-rate estimate. The long field enumeration sentence is dense, but every clause still scans as usage-relevant context rather than padding.

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 the returned field list is supplementary; the description covers scope restriction, ordering, pagination, and the reliability caveat on opens. The main gap is the relationship to readCampaign and the absent default limit, but nothing is left that would cause a mis-call.

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 75% with cursor, status, and workspaceId documented in-schema; the description only echoes the semantics of `status` and the `next`/cursor value. It adds no shape or constraint information beyond what the schema already provides, so baseline 3 applies.

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 resource ('the workspace's campaigns'), its ordering ('newest first'), and the fields it returns, so an agent knows this is a paginated campaign list. It never distinguishes itself from the sibling readCampaign (single-campaign read), which is the one obvious confusion risk, so it stops short of a 5.

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 a real precondition — 'Only for a workspace with subscribed email contacts' — plus a note that `status` keeps one kind and `next` pages, so the agent knows the filtering/pagination model. It does not route the agent to alternatives such as readCampaign for one campaign or readPerformance for aggregate metrics.

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