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

No annotations are provided, so the description must carry the disclosure burden. It discloses the Proof account requirement, the authentication prerequisite, and that start_login is not an entry path. However, it does not state whether the preview is fully non-mutating beyond 'before saving', nor does it describe any output format or side effects.

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 concise and front-loaded with the core purpose in the first sentence. The access paragraph is useful and earns its place, though embedding client-specific authentication instructions slightly reduces the elegance of the tool definition.

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?

With no annotations and no output schema, the description covers the key prerequisite and intended use phase, but it leaves ambiguity about what 'sample data' is, what the preview return looks like, and how this tool differs from render_template or preview_profile_template. An agent can likely invoke it correctly, but selection confidence would be better with a sibling comparison.

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 the baseline is 3. The description adds only high-level context by mentioning placeholder variables being filled in, which helps understand the body/message_type relationship, but it does not add field-level meaning beyond 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 clear action ('Preview a template') and a concrete expected result ('Shows how the message will look with placeholder variables filled in'). The qualifier 'before saving' helps distinguish it from template creation/update or final rendering, though it does not explicitly name sibling tools.

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?

It gives an explicit usage context—use it to preview before saving—and includes a practical access workflow: authenticate via /mcp, then call again. It also warns that start_login does NOT open this tool, which prevents a likely misuse. It does not compare against render_template or preview_profile_template, but the context is reasonably clear.

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