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

With no annotations, the description carries the burden. It discloses that this is a non-saving preview using sample data, that a Proof account is required, and that start_login does not open the tool. It could be more explicit that no mutation occurs, but 'before saving' and 'preview' make the read-only intent clear.

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 short, front-loaded with the purpose, and each block earns its place, including the access warning. The 'ACCESS' paragraph is a little environment-specific but is not bloated.

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 preview tool with fully documented parameters and no output schema, the description covers what it does, when it should be used, and the authentication prerequisite. It does not spell out the return format or error cases, but the stated behavior is enough for correct invocation.

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 schema already documents all seven parameters including enums and length constraints. The description adds only the generic notion that placeholder variables are filled in, which is not enough to move above the baseline.

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 ('Preview') and resource ('profile template') and adds the key purpose 'with sample data before saving', plus the effect 'Shows how the message will look with placeholder variables filled in.' This distinguishes it from generic siblings like preview_template and render_template.

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 a clear usage context ('before saving') and a concrete access requirement: authenticate the client, then call again; start_login does NOT open this tool. It does not explicitly route to alternatives such as preview_template or render_template, so it stops short of a 5.

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