preview_template

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

With no annotations available, the description carries the full burden of behavioral disclosure. It does well by indicating this is a non-saving preview, showing that sample data is used, and describing the auth requirement. It does not explicitly state that no message is sent or that no template is persisted, but 'before saving' strongly implies it.

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 description is front-loaded with the core purpose and then gives actionable access guidance. It is compact, but the first two sentences are slightly redundant ('Preview a template with sample data' and 'Shows how the message will look with placeholder variables filled in'), and the access instructions take a few extra words than necessary.

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 non-mutating preview tool with a fully documented schema, the description covers the essential points: what it does, when to use it, and what authentication is required. It does not explain the output format or explicitly route agents to render_template for saved templates, but those gaps are minor given the tool's simplicity.

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?

The schema already provides 100% coverage with meaningful descriptions for every parameter and enums for channel and message_type. The description adds only general context about placeholder variables and sample data, not parameter-specific guidance beyond the schema, so the 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?

The description clearly identifies the verb ('Preview a template') and the resource, and explains the output: how the message will look with placeholder variables filled in. However, it does not distinguish preview_template from sibling tools like render_template or preview_profile_template, so it misses the top score.

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 gives clear usage context by saying 'before saving' and provides explicit access prerequisites: a Proof account, PROOF_API_KEY, and a server restart. It even warns that start_login does not open this tool. It does not explicitly name alternative tools or when to use them instead, leaving a small gap.

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