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

Annotations already include idempotentHint: true, but the description adds crucial context: duplicate URLs are REFUSED with site_exists rather than silently returned, and retries replay the first result. It also reveals the response contains a tracking code, which is beyond the schema and 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 front-loaded with the primary action and return value, then adds response example, constraints, and follow-up guidance. It's dense but not overly long; the example response is arguably extra but useful for understanding the output shape.

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 tool with no output schema, the description provides a partial response example and covers idempotency, duplicate handling, and the recommended next step. It doesn't specify error handling beyond duplicates, but that's not required. Overall it's complete enough for an agent to use correctly.

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 schema already documents all three parameters (url, hobby, timezone) with descriptions. The description adds no new parameter details beyond the schema; it only restates the URL scheme requirement already present. 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 states a clear verb and resource: 'Add a site to this account and get back its id and tracking code.' It distinguishes itself from sibling tools like create_funnel and create_goal by focusing on site creation, and even names the follow-up tool get_tracking_snippet.

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 states when to use it ('Add a site to this account'), when it will refuse (duplicate URL), and what to do next ('Follow with get_tracking_snippet'). It also explains idempotent retry behavior, leaving no ambiguity about invocation context.

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