render_template

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

readOnlyHint=true already covers the safety profile, so the bar is lower, and the description clears it by disclosing the template resolution fallback chain and the auth prerequisite plus an explicit dead-end warning about start_login. It does not describe output shape beyond 'fully rendered message content', but that is minor for a read-only renderer.

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 functional sentence is front-loaded with zero waste, and the access note is separated out so it can be skimmed or skipped. The PROOF_API_KEY/restart sentence is slightly procedural for a tool description but earns its place by preventing a failed call.

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 read-only renderer with no output schema, the description covers resolution logic, inputs, the return value, and the auth gate. What remains unstated — pagination/format of rendered content and behavior when a variable is missing — is modest relative to the structured fields available.

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 channel, message_type, profile_id and each variable. The description only echoes 'with provided variables' and adds no format, required-variable, or fallback behavior beyond what the schema states — the baseline 3 is appropriate.

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 ('Render the template') and adds resolution semantics — the sub-account's custom template, otherwise the default — which an agent cannot get from the name alone. It stops short of distinguishing itself from the closely-named sibling preview_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?

Gives actionable access guidance (needs a Proof account, set PROOF_API_KEY and restart, and start_login does NOT open this tool), which prevents a wasted attempt. However, it offers no guidance on when to prefer this over preview_template, which is the nearest alternative in the sibling list.

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