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

Beyond the annotations (readOnlyHint, openWorldHint, non-destructive), the description discloses valuable behavioral traits: the return contract (id, name, active status), a specific failure mode (non-master Apollo key returns errorType master_key_required), and the prerequisite that a connected integration must exist. This is genuinely additive context an agent needs to handle errors and prerequisites correctly.

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 description is dense but every sentence carries operational value: purpose, return shape, downstream usage, mailbox prerequisite, key-type error condition, and connection prerequisite. It is front-loaded with the core purpose and the later sentences build logically. Slightly long, but no filler.

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 tool with two parameters, a read-only annotation set, and no output schema, this description is remarkably complete. It compensates for the missing output schema by naming the returned fields, covers error conditions, prerequisites, and downstream workflow integration, and the schema handles the remaining parameter semantics.

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% (both provider and workspaceId are documented in the schema), so the baseline is 3. The description adds meaning by explaining that the provider enum is open-ended ('more providers extend the enum'), which is critical given the openWorldHint annotation, and clarifies the provider-parameterized behavior. This goes beyond what the schema alone communicates.

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 verb and resource ('List an external provider's sequences') and immediately scopes it with the provider parameterization (apollo sequences, instantly campaigns). It clearly differentiates from siblings like campaignstack_list_external_email_accounts and campaignstack_list_external_lead_lists by specifying exactly what is returned (sequence id, name, active status).

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 actionable context: it chains the id forward to campaignstack_add_lead_to_sequence or the integration:add_to_sequence workflow node, points to campaignstack_list_external_email_accounts for the Apollo mailbox prerequisite, and states the connected-integration requirement (campaignstack_connect_apollo / campaignstack_connect_instantly). It lacks an explicit 'when not to use' statement against alternatives, but the provided routing makes the intended use clear.

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