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

Adds real context beyond the annotations: the write bypasses double opt-in, existing members are rejected (consistent with idempotentHint=false), calls are throttled, and the underlying route is POST /members. It stops short of describing response payload or what the throttle limit actually is, so a 4 rather than 5.

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?

Leads with a 'WRITE:' marker that front-loads the mutation risk, then packs consent, alternative, dedup, and throttle notes into a short block with no filler. It is dense to the point of being run-on and could be split for scanability, but every clause carries information.

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?

Covers everything an agent needs to call this safely: consent precondition, the opt-in alternative, duplicate handling, volume limits, and the endpoint. With no output schema required and full schema coverage, no material gap remains.

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%, so every parameter including the nested customFields map is already documented and cross-referenced to cyberimpact_list_custom_fields. The description only restates the group_ids role ('put it in the given groups') and adds no syntax, format, or constraint detail beyond the schema.

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?

Names a specific verb and resource ('add a contact as a subscribed member') and pins down the distinguishing behavior: membership is created WITHOUT a confirmation email, i.e. implied consent. That scope statement separates it cleanly from cyberimpact_send_optin and cyberimpact_update_member without opening a schema.

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?

Gives explicit when-to-use ('only for people who really gave their consent (CASL)'), an explicit alternative with its triggering condition ('to ask the person to confirm first use cyberimpact_send_optin'), and a volume-based redirect ('for many contacts use the app's import'). Nothing about tool selection is left to inference.

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