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

Annotations already declare destructiveHint and idempotentHint; the description adds real context beyond them — partial-update semantics ('Only the fields you pass change') and the explicit unsubscribe path that constitutes the destructive case. It does not spell out whether unsubscribing is reversible or what permissions are required, so it falls just short of 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?

Three short sentences, mutation intent front-loaded, then the field semantics, then the alternative route. No sentence is redundant.

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 destructive mutation with no output schema, the description covers what changes, partial-update behavior, and the re-subscribe escape hatch. It omits failure modes (e.g. unknown member id) and confirmation/irreversibility details, which an agent handling a destructiveHint tool would benefit from.

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, but the description adds update semantics the schema cannot express: only supplied fields mutate, and the state enum's purpose (unsubscribed) is framed as an action rather than a bare value. It does not restate custom_fields keying, which the schema already handles well.

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?

Opens with an explicit 'WRITE:' marker and names the specific resource (member) and the exact operations (custom field values, email address, unsubscribe). An agent can distinguish it from laposta_add_member purely from the text.

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 states what is NOT offered here (re-subscribing) and routes the agent to the Laposta app or laposta_add_member upsert, with the condition 'only when they asked for it'. That is a rare, genuinely actionable when/when-not boundary.

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