sendcraft_add_subscriber

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

With no annotations, the description carries the burden. It discloses a key behavioral trait: if double opt-in is enabled, a confirmation email is sent. However, it does not mention duplicate handling, permission requirements, or whether the subscriber becomes active immediately, leaving significant behavioral gaps for a mutation tool.

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 two sentences long, front-loaded with the primary purpose, and every sentence earns its place. It is concise and easy to parse.

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 5 parameters, no output schema, and no annotations, the description is somewhat incomplete. It mentions double opt-in but does not explain the resulting subscriber state (e.g., pending vs. active) or what happens on duplicate email. Schema covers parameters, but behavioral outcomes are under-specified.

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%, so the baseline is 3. The description does not add additional meaning to the parameters beyond what the schema already provides; it only describes the overall action. No extra insight about tags, names, or list_id is given.

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 clearly states the action ('Add a new subscriber/contact to a list') with a specific verb and resource. It distinguishes itself from sibling tools like sendcraft_unsubscribe and sendcraft_list_subscribers by focusing on the add operation, and it adds the double opt-in nuance.

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 implies clear usage: use this when you want to add a new subscriber to a list. It doesn't explicitly mention alternatives or exclusions, but the sibling context makes it obvious this is the creation tool vs. listing or unsubscribing. The double opt-in note provides situational context.

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