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

Annotations already mark readOnlyHint=true and openWorldHint=true, but the description adds substantial behavioral context: robots.txt compliance, refusal of private/internal/oversized/non-HTML content, no bypassing logins/paywalls, untrusted output warning, and the payment-required trigger. No contradiction with 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?

Front-loaded with the primary action and output details, followed by constraints, a safety caveat, and payment behavior. Every clause earns its place, though the density of constraints makes it slightly heavy.

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?

Despite having no output schema, the description enumerates return fields and explains error/refusal conditions, including the payment requirement. For a one-parameter tool, this provides everything an agent needs to call and interpret the result 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 coverage is 100% and the schema description already covers the url parameter thoroughly ('public http(s) page', 'private, loopback and internal addresses are refused'). The description reinforces these constraints and adds related behaviors (oversized, non-HTML), but it does not add new parameter format or semantics beyond the schema.

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?

States a specific verb ('Fetch') and resource ('one public web page') and enumerates the return fields: clean markdown with title, byline, language, word count, and SHA-256. This makes the tool's function precise and differentiates it from the sibling mm_status.

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?

Implies usage for public web pages and lists refusals (private/internal addresses, oversized pages, non-HTML), giving clear context. However, it does not explicitly state when to choose this tool over alternatives or when not to use it relative to sibling tools.

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