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

Annotations only carry openWorldHint and a title, so the description carries most of the load — and it does: ALWAYS forced into test mode, never delivered to a real inbox even with a live key, but rendered and logged for inspection. This is exactly the behavioral context the sparse annotations don't provide.

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?

Three tight sentences, front-loaded with the core action, then the safety guarantee, then the workflow. No filler; every clause adds decision-relevant 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?

With an output schema present, return values need not be explained, and the description covers modes, the never-delivers guarantee, and the read-back path. Nothing an agent needs to invoke this correctly is missing.

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, but the description adds real semantic value by framing templateId+variables and subject/html as mutually exclusive alternatives ('either...or'), clarifying the conditional requiredness the schema only implies.

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+resource ('Render and send a test message') and immediately disambiguates the two supported modes: saved template (templateId + variables) versus ad-hoc (subject/html). An agent can tell this apart from siblings like volanea_render_template and volanea_test_workflow 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?

Gives a clear workflow ('Use it to verify content renders correctly, then read it back with volanea_check_delivery'), naming the follow-up sibling. It lacks an explicit exclusion against the near-neighbor volanea_render_template (render without sending), so a 4 rather than a 5.

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