Add subscriber to sequence by email address

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

Annotations already declare destructiveHint=true, non-idempotent, openWorld, and non-read-only. The description goes beyond them by naming the concrete blast radius ('delivery, audience membership, published data or irreversible state') and restating the confirm gate, which is useful added context for a mutation.

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 short sentences, front-loaded with the action and followed by the impact warning and the confirm requirement. No filler, though the impact sentence is a generic catch-all list rather than specific to this tool.

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 6-parameter, nested-payload mutation with no output schema, the description covers the action, the key, the side-effect risk, and the confirmation gate. Remaining gaps (duplicate-subscription behavior, email vs. payload precedence) are minor.

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 83%, so the schema already documents confirm, payload, payload_file, account, and sequence_id. The description only reiterates the confirm requirement and the email-address lookup, adding little beyond structured fields — the baseline 3 for high coverage is appropriate.

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 ('Add subscriber to sequence') and the lookup key ('by email address'), which implicitly distinguishes it from the sibling add_subscriber_to_sequence_by_id. It does not explicitly name that sibling, but the action is unambiguous.

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?

It states the confirm=true prerequisite, which is genuine invocation guidance, but gives no when-to-use/when-not context and never routes the agent to the alternative 'by_id' sibling. Usage is implied rather than explained.

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