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

With no annotations provided, the description carries the full burden. It usefully discloses that this is render-only with no sending and no credit consumption, which are important behavioral traits. It does not explain return format, error conditions, or that the optional fields it lists are not accepted by the schema.

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?

The first sentence is concise and front-loads the purpose and safety profile. The second sentence is less effective because it spends most of its length listing optional parameters that are not in the schema, undermining the value of that sentence.

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 simple one-parameter preview tool, the description gives the essential purpose and non-sending behavior. However, with no output schema, it could better explain what the rendered preview returns, and it references unsupported optional parameters that are not part of the tool contract.

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 schema already documents the single required 'id' parameter as the agent id. The description instead introduces optional fields such as mode, prompt, tone, customInstructions, variant, followUp, and sample, none of which exist in the input schema and which additionalProperties=false would reject. This creates misleading parameter semantics rather than supplementing 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?

The description states a specific verb and resource: render a sample outreach email from an agent. It also clarifies that nothing is sent and no credits are used, which helps an agent understand the operation. It names preview_campaign_email as equivalent but does not clearly differentiate when this tool should be chosen over that sibling.

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 implies this is a preview-only operation and explicitly says 'no sending, no credits.' It also says it behaves like preview_campaign_email, which gives some context. However, it does not state when to use this tool versus preview_campaign_email, crm_preview_email_to_lead, or other preview siblings.

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