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

Annotations already disclose readOnly=false, destructive=false, idempotent=false, openWorld=true. The description adds real behavioral context the annotations can't: the campaign must have content and must not already be sent, and the write only reaches one address. It doesn't state likely failure modes or error behavior.

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?

Two sentences with zero waste. The "WRITE:" prefix and the main action are front-loaded, and the negative scope statement follows immediately.

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 2-parameter write with no output schema, the description covers preconditions, target, and scope of effect. Only the response/confirmation behavior is unaddressed, which is a minor gap.

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 both parameters are already documented, including the campaign_id provenance from laposta_list_campaigns. The description only reinforces the single-recipient constraint ("ONE email address"), so the baseline of 3 applies.

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?

A specific verb plus resource ("send a test copy of a campaign") with explicit scope ("to ONE email address") and a negative clarifier ("Does not send the campaign to its recipients"). An agent can distinguish this from laposta_create_campaign or laposta_get_campaign without opening any 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?

The description establishes the context of use — verifying a campaign that already has content and hasn't been sent — which is a clear eligibility condition. It does not name a competing/alternative tool, so it stops short of full when-to-use guidance.

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