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

Annotations (readOnlyHint=false, destructiveHint=false) are consistent. Description adds behavioral details beyond annotations: max 5 webhooks per account, payloads HMAC-SHA256 signed, and the need to save the returned secret. This fully informs the agent.

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 cover purpose, events/limit, and signature handling. No extraneous words, but could be slightly more structured (e.g., separating behavioral notes). Still well within good conciseness.

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 simple 2-parameter tool with no output schema, the description covers all necessary context: purpose, events, account limit, and post-creation action. No gaps identified.

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?

Input schema has 100% coverage with clear descriptions for url and events. The description does not add significant meaning beyond the schema's enum and descriptions, so baseline of 3 is appropriate.

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 clearly states 'Create a webhook subscription for event notifications,' lists specific events (screenshot.completed, quota.warning, quota.exceeded), and mentions the account limit of 5. This distinguishes it from sibling tools like delete_webhook and list_webhooks.

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?

Provides explicit context: available events, maximum webhooks per account (5), and instruction to save the returned secret for signature verification. Does not explicitly state when not to use, but the creation context is clear.

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