Update subscriber

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

Annotations already declare readOnly=false, destructive=false, idempotent=false, openWorld=true, so the safety profile is carried. The description adds real value beyond them: it discloses partial-update semantics and, critically, that passing list_ids performs a wholesale replacement of memberships — a destructive-in-effect behavior not signaled by destructiveHint=false. It stops short of noting that preconfirm or status changes may trigger external side effects.

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, no filler, with the partial-update rule front-loaded before the list_ids caveat. Tight and each sentence carries information, though the opening "Update a subscriber" restates the title.

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 7-parameter mutation with zero schema descriptions and no output schema, the description should say more about the remaining fields. It covers the two highest-risk behaviors well, but preconfirm (likely controls confirmation email sending — an externally visible side effect), attribs merge semantics, and valid status transitions are left entirely to inference.

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 0% across 7 parameters, so the schema alone conveys only types and the required `id`. The description compensates for the single most dangerous parameter (list_ids = replace) but says nothing about status enum transitions, the nested attribs merge behavior, or what preconfirm actually controls. Partial compensation, not full.

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?

States a specific verb and resource ("Update a subscriber") and carves out the list-membership case by naming the sibling subscribers_lists_change. That differentiation is partial — it only distinguishes this tool from one of the three sibling subscribers_* tools — but an agent can still identify the operation.

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?

Explicitly says "Only the fields you pass change", which tells the agent this is a partial/PATCH-style update rather than a full replace. It also gives a concrete routing rule: use subscribers_lists_change when you want to add/remove without replacing. No when-not guidance for other siblings (e.g. vs subscriber_create), but the core selection logic is covered.

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