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samirsaci

mcp-webscraper

by samirsaci

extract_first

Extract the first element matching a CSS selector from a webpage to retrieve specific content such as title or heading.

Instructions

Extract the first matching element from a webpage.
Useful for getting single values like page title, main heading, etc.

Args:
    url: The webpage to scrape
    css_selector: CSS selector for the element (e.g., "h1", "title", "meta[name='description']")
    attribute: What to extract - "text" for content, or attribute name like "href", "content", "src"
    javascript: Set to True for JavaScript-rendered sites

Returns:
    Dictionary with the extracted value

Example:
    extract_first(url="https://example.com", css_selector="title", attribute="text")

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
urlYes
css_selectorYes
attributeNotext
javascriptNo

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes
Behavior3/5

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

With no annotations, the description carries the full burden. It mentions javascript handling for rendered sites and return format, but omits error handling, what happens on no match, or limits.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is concise yet complete, using bullet-point Args, Returns, and an Example. Every sentence serves a purpose, with no wasted words.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's simplicity, the description covers all necessary aspects: parameter semantics, return value, and usage context. The example solidifies understanding.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters5/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 0%, so the description fully compensates by explaining each parameter, including defaults, examples, and attribute choices. This adds substantial value beyond the bare schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states 'Extract the first matching element from a webpage' with a specific verb and resource. It provides examples and contrasts with batch operations, effectively distinguishing from sibling tools.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly states it is for single values like page title or heading, giving clear context for when to use. However, it does not explicitly mention when not to use or directly reference sibling alternatives.

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

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