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

Annotations cover only hints (readOnlyHint=false, openWorldHint=true), so the description usefully adds the critical operational fact that each successful call costs $0.001 in USDC on Base via x402 — a prerequisite an agent must know before invoking. It also describes the return shape, though it does not explain failure/refund behavior for unsuccessful calls.

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?

Two sentences, both front-loaded and waste-free: the first defines the output decomposition, the second covers usage and cost. The long output enumeration is informative rather than padding, though it is dense enough to be mildly scannable-unfriendly.

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?

There is no output schema, so the description correctly compensates by enumerating the returned fields and noting the IP-host flag. Combined with the payment disclosure, an agent has what it needs to call the tool correctly; only edge cases (malformed URL handling) are unaddressed.

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 100% with a single required 'url' parameter already documented in the schema. The description adds no format, encoding, or validity constraints beyond what the schema states, so the baseline 3 applies.

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 ('Split') plus resource ('a URL') and enumerates the exact decomposition produced: protocol, host, port, path, query params object, hash, origin, plus IP-address detection. An agent can distinguish it immediately from siblings like url_encode, url_decode, and domain without opening any schema.

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?

'Use to read query parameters or check a link's host' gives concrete triggering scenarios, which is more than most definitions offer. It stops short of naming an alternative tool or stating when not to use it, so it does not reach the 5 tier.

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