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

Annotations already declare readOnlyHint=true/destructiveHint=false, and the description adds substantial behavioral context beyond that: the exact return shape (raw vs personalized body, detected merge tags), the dual-mode behavior (providing a sample user vs omitting both params yields raw tags only), and sample_user_id priority semantics. No output schema exists, so this behavioral disclosure carries real weight.

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 sentences, each earning its place: purpose, return values, then workflow/parameter guidance. Zero fluff, and the most decision-relevant fact (call before send_test_template) is prominently placed.

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?

Complete for a read-only preview tool: no output schema exists, but the description explains return values; the required param is documented in schema; the two personalization modes are covered; and the relationship to its workflow sibling is explicit. The only conceivable gap (behavior on unresolvable sample_user_email) is a minor edge case.

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%, and the individual parameter descriptions are rich (example subject line, tenant-scoped email lookup, priority ordering, omit-to-get-raw behavior). The description mostly restates what the schema already says about sample_user_id/sample_user_email, adding a compact framing but no genuinely new parameter insight.

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?

Starts with a specific verb+resource+mechanism ('Preview a template with merge tags resolved against a sample user's profile'), which immediately distinguishes it from siblings like nevent_get_template (fetch), nevent_update_template (mutate), and nevent_send_test_template (send). The return values (originalBody, personalizedBody, detectedMergeTags) further pin down what the tool does.

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 explicit workflow guidance: 'Always call before nevent_send_test_template to validate rendering.' This tells the agent when in a sequence to use the tool. It does not explicitly state when NOT to use it or name routing alternatives such as nevent_get_template for plain template retrieval, but the sequencing rule is clear and actionable.

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