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

Beyond the annotations, the description discloses major behavioral consequences: causes real emails to be sent, is not recallable once steps go out, and writes into a shared workspace with no per-caller isolation. These are exactly the non-obvious side effects an agent needs before calling.

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?

Four focused sentences, each earning its place. The warning is front-loaded, the prerequisite is stated concretely, and the shared-workspace caveat adds essential context without 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 complex, destructive tool, the description covers the non-obvious inputs: where to fetch the sequence id, how the sequence must be confirmed, what side effects entry triggers, and how writes are shared. An output schema covers the return value, so no further explanation is required.

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 description coverage is 100% and every parameter has a description. The description adds no new parameter-level meaning, so the baseline of 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?

The description opens with a specific verb and resource: 'Add contacts to an email sequence.' It immediately distinguishes this from look-up siblings by warning that this endpoint triggers real email sending, which clarifies its unique role among the many search/read tools.

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 prerequisite: obtain the sequence id from post_apollo_emailer_campaigns_search and confirm its state before adding anyone. It does not explicitly contrast with alternatives like the remove/stop sibling, but it clearly signals that this tool should only be used when sending is intended.

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