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

Beyond the annotations (mutation, non-idempotent, non-destructive), the description discloses the default events, the returned fields, validation_error failure for bad URLs or short secrets, and implies duplicate registration is not deduplicated by advising a list_webhooks check. No contradiction with annotations.

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 compact sentences front-load the core purpose and immediately give routing guidance, defaults, return values, and failure modes. Every sentence earns its place with no filler or repeated schema content.

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?

Despite having no output schema, the description enumerates the returned fields (id, url, events, is_enabled, created_at) and the main validation failures. Combined with full schema coverage and sibling routing, an agent has everything needed to invoke and interpret the result.

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?

The input schema already documents all four parameters (100% coverage), so the baseline is 3. The description adds value by spelling out that URL must be valid http(s), that defaults are pin.published and pin.failed, and the secret length rule tied to validation_error, though it partially duplicates schema constraints.

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 description opens with a concrete verb and resource ('Register an endpoint PinBridge calls when a pin publishes or fails'), and the sibling comparisons ('Check list_webhooks', 'use update_webhook') make it distinct from other webhook tools. No ambiguity about what this 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?

It explicitly says to use this instead of polling get_pin when callbacks are possible, tells the caller to check list_webhooks first to avoid duplicate URLs, and routes changes/pausing to update_webhook. This is explicit when-to-use and when-not-to-use guidance with named alternatives.

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