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

Annotations already declare readOnlyHint=false, openWorldHint=true, idempotentHint=false, destructiveHint=false; the description adds genuinely new context on top: campaign state is unaffected despite the WRITE label, and the sender must be verified. It omits what happens on an unverified sender (error vs silent fail) and any rate limits, so it is strong but not exhaustive.

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?

Four short sentences with zero filler; the WRITE marker and the core action are front-loaded, followed by the two behavioral constraints. Every sentence carries distinct 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?

For a two-parameter, non-destructive-per-annotations write tool with no output schema, the description covers action, scope, state impact, and the sender prerequisite. The only gap is what the call returns or how a test email is distinguished (e.g., subject prefix), which is minor here.

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 both campaign_id and email are already documented in the schema. The description only reinforces 'single address' and 'a campaign', adding no format, id-source, or validation detail beyond what the schema provides; baseline 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?

States a specific verb and resource ('email ONE test copy of a campaign to a single address') with the key scoping constraint that it is a single test recipient. The phrase 'test copy' plus 'campaign state does not change' distinguishes it from emailchef_send_campaign and emailchef_send_email without needing to open the 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?

'ONE test copy' and 'The campaign state does not change' clearly frame the tool as a pre-send verification step rather than a real send, which implicitly routes the agent away from send_campaign. It stops short of explicitly naming the alternative tool or stating exclusions, so it is clear context rather than a full when/when-not rule.

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