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

Annotations already establish a safe read (readOnlyHint=true, destructiveHint=false, openWorldHint=false), and the description adds genuinely new behavior: default page size, the returned field set, and a full account of healthScore — its 0-100 scale, direction, daily movement, and the exact conditions under which it is null. That null-semantics detail is the kind of thing an agent cannot get from annotations or schema and would otherwise misread as zero.

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 page size before the filter options and the healthScore explainer, and every sentence carries information. The healthScore sentence is dense but earns its length because it defines a non-obvious computed field; a small trim would still keep the meaning.

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 takes on the job of describing returns and does so for the important fields, plus pagination defaults. Five optional filters and no required params are handled adequately. It could say a bit more about ordering or the remaining returned attributes, but nothing essential to a correct call is missing.

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% and each parameter already carries a description, including the spaceId cross-reference to list_workspaces, so the schema does the heavy lifting. The prose restates the same three filters (campaign, connection state, workspace) without adding format, interaction or edge-case semantics such as what happens when campaignId and spaceId conflict. 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 verb and resource ('Lists the sending email accounts in the workspace') and immediately names what comes back: connection status, daily limits and health score. The plural/list scope and per-page framing make it clearly distinct from the single-record get_sender_email and from mutation siblings like update_sender_email.

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 an explicit use case ('Use it to pick the accounts to add to a campaign') and maps each filter to the reason for using it: campaign senders, connected vs disconnected mailboxes, or a single workspace. It stops short of naming the sibling to prefer for other jobs (e.g. get_sender_reputation for account-level metrics), so it is clear but not fully exclusive.

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