assert_url_contains

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

With no annotations provided, the description appropriately discloses the key behavioral trait: it raises an exception if the substring is not found within 7 seconds. This goes beyond the basic assertion semantics and tells the agent about the timeout and failure mode.

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 two short sentences with no filler or redundant information. The core assertion is stated first, and the failure behavior is placed immediately after, making it easy to parse quickly.

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 one-parameter assertion tool with an output schema available, the description covers the essential behavior, the failure mode, and the timeout. It is slightly incomplete because it does not distinguish itself from the similarly named assert_url sibling, but this is a minor gap for such a straightforward tool.

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?

The schema provides only the parameter name 'substring' with no description, but the tool description clarifies that the substring is the expected value to search for in the current URL. This adds meaningful semantic context to the single required parameter, though it does not discuss case sensitivity or matching details.

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 that the tool asserts the current URL contains a given substring, and it defines the exact condition being checked. It does not explicitly contrast itself with the sibling assert_url tool, so it loses the last point for sibling differentiation.

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 does not say when to prefer this tool over assert_url, wait_for_text, or other URL-checking tools. No usage context, prerequisites, or alternatives are mentioned, leaving the agent to infer appropriate timing from the tool name and behavior.

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