render_sms_template[read] Fill a template (sms_template_id or sms_template_uuid) with sms_message_vars and report the resulting text, its segments and any missing variables. Sends nothing.
| Name | Required | Description | Default |
|---|---|---|---|
| sms_template_id | No | ||
| sms_message_vars | No | ||
| sms_template_uuid | No |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description still adds SDK-specific value by stating "Sends nothing" and by enumerating what the call reports (rendered text, segment count, missing variables) — the segment/missing-variable outputs are non-obvious behavior not derivable from annotations.
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?
Two sentences with a leading [read] tag, the render action front-loaded, then the outputs and the no-send guarantee. No redundant restatement of the tool name or annotations.
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 output schema, the description correctly enumerates what is returned (text, segments, missing variables), which is exactly what an agent needs. It omits edge behavior such as what happens when neither template identifier is supplied, but that is a minor gap for a simple three-parameter read tool.
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 0%, so the description must carry the load, and it does name all three parameters in context: the template may be addressed by numeric id or UUID, and the vars object supplies placeholder values. It does not clarify requiredness (all three are optional in the schema, which is odd) or that vars keys must match template placeholders.
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 names a specific verb (fill/render) and resource (SMS template), states the two inputs consumed, and explicitly says the result is reported rather than sent. An agent can distinguish this from send_sms and list_sms_templates without opening any schema.
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?
"Sends nothing" plus "report the resulting text... and any missing variables" gives clear context that this is a preview/dry-run tool. It stops short of naming the sibling to use when actually sending (send_sms), so the routing advice is implied rather than spelled out.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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