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

Annotations are minimal (readOnlyHint false, destructiveHint false, etc.), so the description carries the burden. It discloses important behavioral traits beyond the schema: the endpoint is always restricted to the authenticated user's account IDs, and by default matching future accounts are automatically included. This adds security and default-behavior context that annotations do not provide, though it omits details about failure modes or return values.

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 description consists of four tightly packed sentences, each adding value: purpose/security, auto-include default, and n8n validation workflow. It is front-loaded with the core action and scoping. No filler or repetition; slightly dense but appropriately concise for the amount of context.

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 create tool with 7 parameters and no output schema, the description provides important security and workflow guidance but leaves gaps. It does not state what the tool returns (e.g., created destination ID) or how errors are surfaced. It also does not explain runtime values or reiterate the events enumeration guidance (though schema covers that). Overall, the description is helpful but not fully complete for an agent to confidently call without additional lookups.

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 only 57%, so the description should compensate. It does add meaning to auto_include_new_accounts ('By default matching future accounts are automatically added') and to request_url ('For n8n use its Test URL first...'), but it does not clarify name or runtime semantics. The events and providers parameters already have descriptions in the schema, so the overall contribution is partial rather than comprehensive.

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: 'Create a realtime event destination for this Nilyo user.' The security scoping detail ('restricts the Unipile endpoint to account IDs owned by this authenticated user') differentiates it from generic webhook creation and from sibling tools like webhook_update_destination or webhook_test_destination. The purpose is unambiguous and actionable.

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?

The description gives a concrete n8n workflow ('use its Test URL first, validate with a Development/Mock event, then update to Production URL'), which is useful context. However, it does not explicitly state when to prefer this tool over alternatives like webhook_update_destination, nor does it mention exclusions such as 'use webhook_get_setup_guide to learn more.' The intended usage is implied but not contrasted with siblings.

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