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

Annotations already declare readOnlyHint=true, openWorldHint=false and destructiveHint=false, so the safety profile is covered. The description adds genuinely new behavioral detail: the conditional presence of `records` (only while the domain is unverified) and the semantic difference between rolling 24h `sentToday` and lifetime `sharedTrial.sendsUsed`, which preempts a likely misinterpretation. No pagination/rate-limit detail, but none is needed for a status read.

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 tight sentences, front-loaded with the resource scope, then conditional behavior, then the clock-semantics clarification. The `sentToday` vs `sharedTrial.sendsUsed` sentence is slightly dense but each sentence earns its place by preventing a concrete misreading.

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 zero-required-param read tool with full annotation coverage and no output schema, the description covers scope, the conditional `records` field, and non-obvious counter semantics. Minor gap: it does not characterize the reputation field's shape, and with no output schema the agent gets no return-value guidance beyond the field names mentioned.

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 the single optional `project` parameter is fully described in the schema (id from list_projects, runs in that project vs. connection default). The description adds nothing about the parameter, 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?

Names a specific verb (read) and a specific resource (sending status), then enumerates what that status comprises: readiness, domain verification, daily usage, reputation. The closing "Does not send mail" plus the read-only framing distinguishes it from siblings like read_integration_delivery_status and read_plan_usage.

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?

Usage context is implied: an agent consulting sending readiness / domain verification should call this, and the note that `records` only appears while unverified tells the agent when that branch is meaningful. However, there is no explicit when-to-use guidance and no named alternative among the many read_* / list_* siblings, so the agent must infer routing.

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