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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior. The description adds meaningful behavioral context beyond those hints: the notion of per-account state ('sending limits and per-account state') and the operational consequence of unhealthy mailboxes, which is valuable for an agent deciding whether a sequence is ready. No contradiction with annotations.

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 sentences with no fluff: the first identifies the resource and return payload, the second confirms no parameters and adds a practical usage tip. Every sentence earns its place and the key information is front-loaded.

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 no-parameter, read-only, idempotent tool with an output schema, the description covers everything an agent needs: what it returns, that it requires no arguments, and when to invoke it in a sequence workflow. Nothing essential 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?

The tool has zero parameters, so the schema provides no explanatory burden. The description explicitly states 'Takes no parameters,' removing any ambiguity about hidden or optional inputs, fully covering parameter semantics for an agent.

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 specific resource ('mailboxes connected to this workspace') and the return shape ('email_accounts array with sending limits and per-account state'), making it clear this is a list/read tool for email accounts. It is distinct from siblings like get_apollo_accounts_id or get_apollo_users_search because it explicitly identifies mailboxes rather than org accounts or users.

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?

The description gives a concrete trigger: 'Check it before activating a sequence' and explains the consequence (a sequence without a healthy mailbox won't send). It provides clear context for when to use it, though it does not explicitly name alternatives or exclusions, which keeps it one step below the top score.

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