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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the description earns credit for adding context the agent would not otherwise have: 'render' returns exactly what a recipient would see and 'nothing is sent', and 'get' returns subject, body and versions. It never contradicts the annotations, though it doesn't cover error cases or limits on the sample-variable rendering.

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?

One long, dense paragraph that front-loads the resource and then walks the actions in order, with zero filler sentences. The run-on framing ('action list: ... get: ... render: ...') is slightly compressed but still scannable and every clause carries actionable information.

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 9-parameter tool with no output schema and a nested variables object, the description covers the resource, all three action modes, and roughly what comes back from get and render. It omits what a list entry contains and how variables are bound to placeholders when a version is not specified, which keeps it short of a 5.

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 coverage is 100%, so the baseline is 3; the description beats that by mapping parameter combinations to actions ('render: fill a template (slug, optionally a version) or unsaved subject/html/text'), which tells the agent that slug and unsaved fields are mutually exclusive alternatives for render — a relationship the flat schema does not express.

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 first sentence names the resource precisely ('workspace's saved email templates') and the description then enumerates the three verbs (list, get, render) with what each does. It's distinguishable from email_drafts/email_sent by the 'templates' framing, but it never explicitly contrasts with those siblings, so it stops short of a 5.

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?

'render' is clearly framed as a preview ('nothing is sent'), which implies when to use it rather than email_send. However, there is no explicit when-to-use/when-not-to-use guidance, and no routing statement distinguishing this tool from email_drafts or email_campaigns, leaving the agent to infer.

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