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

The description discloses that it is a 'State-changing external action' and that it occurs 'after authorization,' which adds context beyond the annotations. Since annotations already indicate readOnlyHint=false and destructiveHint=false, the description's additional note about authorization and external impact enhances transparency without contradicting the 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?

The description is concise, consisting of three clear sentences. It front-loads the primary purpose ('change a webhook...') and immediately follows with essential constraints ('Requires subscription_id...', 'use list-webhook-events...'). No unnecessary words or redundant information.

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?

Given the tool's moderate complexity (5 parameters, including a nested object) and lack of output schema, the description covers all necessary context: what it does, when to use it, required inputs, and references to related tools. It provides enough information for an agent to select and invoke the tool correctly without additional documentation.

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 coverage is 100% with descriptions for all parameters. The description adds context by telling users to obtain subscription_id from list-webhook-subscriptions and to use list-webhook-events for valid keys, which helps understand the relationships between parameters and other tools. This goes beyond the schema's basic definitions.

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 the tool's purpose: to change a webhook endpoint URL, subscribed events, active/inactive status, or metadata. It explicitly mentions 'updates the webhook subscription' and distinguishes from create/delete by focusing on modifications. The reference to requiring subscription_id from list-webhook-subscriptions and using list-webhook-events for valid keys further clarifies its role among related tools.

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 explicitly states when to use the tool ('Use this when the user wants to change...') and provides prerequisites: 'Requires subscription_id from list-webhook-subscriptions' and 'use list-webhook-events for valid keys.' This gives clear guidance on when to invoke it and what to prepare, which is more than sufficient.

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