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

Beyond the minimal annotations, the description discloses a critical behavioral side effect: 'CHANGES WHERE YOUR DATA IS SENT: every future signal matching the routing rule will be delivered there.' It also adds a constraint ('Subject to your plan's destination limit') and a validation requirement ('config must match the shape for the chosen type'). This is exactly the kind of behavioral context the annotations do not provide.

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 compact and every sentence earns its place: the core creation action, the destination-type examples, the critical side-effect in an attention-grabbing caps phrase, the config-type coupling, and the plan-limit caveat. No filler or redundant restatement of the name/title.

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 description covers the main points an agent needs before calling: what the tool does, the important routing side effect, the config/destinationType dependency, and the plan limitation. An output schema exists, so return-value details are not required. It slightly under-specifies comparison with update_destination and does not mention all enum values, but those are minor given the schema and sibling names.

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?

Even though the schema has 100% description coverage, the tool description enriches the parameters by linking config to the chosen destinationType ('config must match the shape for the chosen type') and clarifying the routing parameter's behavioral effect ('every future signal matching the routing rule will be delivered there'). This goes beyond the schema's generic descriptions.

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 states a specific verb and resource: 'Create a new place for signals to be delivered' and then elaborates with concrete destination types (Slack, webhook, Google Sheet, n8n, Clay, Notion). It distinguishes from update_destination by emphasizing 'new' and from read tools by describing creation. The purpose is unmistakable.

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 implies the tool is for creating a new destination and explains the effect on future signal routing, giving clear context. However, it never explicitly says when to use this instead of sibling tools like update_destination or list_destinations, and there are no stated exclusions or alternative tool mentions. Usage is inferred, not spelled out.

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