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

Annotations already declare readOnly=false, destructive=false, and idempotent=false. The description adds useful behavior beyond that: deliveries for other resources are unaffected, and the endpoint must already exist. This helps the agent understand the operation's scoped side effects without repeating annotation fields.

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 sentences with high information density. The core purpose and scoping constraint are front-loaded, the alternative is named, and the documentation requirement is appended without fluff.

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?

The tool has 6 required parameters, but 100% schema coverage and an output schema cover structured details. The description supplies the missing contextual layer: when to use it, what scope it affects, and where to get configuration rules and event catalogs. Nothing critical is left unaddressed.

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 adds meaning by clarifying that only one resource per subscription is allowed, defining the resource family (extractor/classifier/splitter/workflow), and linking to the event catalog that informs valid enabledEvents values.

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?

Description states a specific action ('Subscribe an existing webhook endpoint') and precisely scopes the resource to 'ONE specific extractor, classifier, splitter, or workflow'. It clearly distinguishes this from creating an endpoint and from the sibling create_webhook_endpoint tool.

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?

Explicitly says 'Use this instead of global enabledEvents when only some resources matter', giving a clear when-to-use condition and a named alternative. It also provides a prerequisite action by instructing the agent to call get_documentation with the configuration URL first.

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