probe_selectors

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

With no annotations, the description carries the full burden. It explains the basic behavior and output shape (match counts and a sample of the first match), but it does not disclose potential fetch failures, dynamic content limitations, or whether the operation is purely read-only. This is adequate but not rich.

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 concise sentences with no wasted words. The primary action is front-loaded first, followed by a clear usage recommendation. It is appropriately sized for its purpose.

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 two-parameter tool with no output schema, the description gives a reasonable overview and states return behavior. However, it lacks details about the structure of the 'selectors' items, possible error behaviors, and how this tool relates to the sibling tools. It is minimally complete but leaves gaps an agent must infer.

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 0%, so the description must compensate. It explains the general role of selectors, but it never defines the required 'name'/'css' fields or the optional 'attribute' field, which the schema leaves only minimally documented. This is a notable gap.

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 identifies the action ('Fetches a web page') and the resource ('for each CSS selector... how many elements match'), making the tool's core function easy to grasp. It does not explicitly contrast itself with sibling tools like discover_selectors or inspect_page_structure, so it falls short of a 5.

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 phrase 'Use it to verify or refine candidate selectors cheaply' gives clear context for when the tool is appropriate. However, it does not mention when not to use it or name alternative tools, leaving some routing decision to the agent.

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