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

Annotations cover the safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=true, idempotentHint=false), so the bar is lower. The description still adds real behavior: MailerCloud pushes the chosen events outbound to the URL, and dry_run provides a non-mutating validation path. Remaining gaps are permission/ownership requirements and whether the URL is verified before activation.

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 tight sentences, front-loaded with the action and outcome, then the required inputs, then the optional validation flag. The required-field list is somewhat redundant with the schema but is cheap and readable.

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 4-parameter create tool with full schema coverage and annotations, this is nearly sufficient: it says what is created, what inputs are mandatory, and how to test safely. It stops short of covering URL verification, permission requirements, or post-creation state, and there is no output schema so return values are untouched.

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%, so the baseline is 3. The description restates the required trio (name, url, events) rather than enriching it, though the 'https' constraint on the URL is a real addition the schema's plain 'Webhook URL' does not convey.

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?

Specific verb + resource ("Create a new webhook") plus the outcome ("to receive event notifications"), which tells an agent what it gets. It does not differentiate from the sibling create_transactional_webhook, so an agent must infer which webhook type applies.

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 dry_run guidance ("Set dry_run: true to validate without creating") is a genuine usage recommendation, which is more than most create tools offer. However, there is no statement about when to use this versus create_transactional_webhook, test_webhook, or update_webhook, leaving sibling selection to inference.

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