URL Safety Validator MCP

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

With no annotations provided, the description carries the full burden. It discusses the services checked (Google Web Risk, Safe Browsing), the returned verdict structure (including agent_action, trust score, threat categories), and a warning about the irreversibility of payment fraud on phishing domains. It also states that a DANGEROUS verdict means halt immediately and that no further analysis is needed. This is highly transparent.

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 relatively long but each sentence serves a purpose. It front-loads the main action and then provides context and warnings. Minor redundancy (e.g., repeating 'payment executed on a phishing domain') could be trimmed, but overall it is well-structured and efficient.

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?

Given the tool is simple (one required parameter) and has an output schema (implied by the return description), the description covers all necessary aspects: what it checks, against which services, what the verdict includes, and when it's critical to use it. The warning about payment recovery adds essential context. It feels complete.

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 description coverage is 100% (single 'url' parameter with a clear description). The description does not add additional semantic details beyond what the schema provides (e.g., it mentions 'Full URL preferred' but the schema already states that). Therefore, baseline score 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 specific verb ('Checks a URL') and resource ('for phishing, malware, typosquatting, and redirect threats'), clearly defining what the tool does. It differentiates from potential similar tools by specifying the threat categories, and there are no sibling tools to confuse.

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 explicitly says when to call this tool ('BEFORE your agent fetches, follows, or forwards any URL') and provides concrete scenarios ('merchant site, supplier portal, or payment redirect URL'). It also specifies the context of receiving a URL from an external source. This gives clear guidance without ambiguity.

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