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

Annotations only cover safety flags (readOnlyHint=false, openWorldHint=true, idempotentHint=false, destructiveHint=false); the description adds genuinely new operational context by stating the tool costs $0.001 in USDC on Base via x402 and is charged 'per successful call'. That payment/reversibility detail is exactly the kind of thing annotations cannot express, though it says nothing about failure modes or latency.

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?

Three tight sentences: what it does first, when to use it second, cost last. No filler, no repetition of the schema, and the most decision-relevant facts are front-loaded.

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?

With no output schema, the description carries the burden of describing the return value, and it does so at a useful level ('each line marked as unchanged, removed or added, with counts'). Cost and usage context are covered; the only minor gap is the concrete output format (structured JSON vs. unified diff) for a 2-param tool.

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%, so 'The original text' (a) and 'The new text' (b) are already documented; the description only implies the two-input shape without mapping which parameter is the original versus the new version. Baseline 3 applies since the schema does the heavy lifting.

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 concrete verb+resource ('Line-by-line difference between two texts') and even previews the output shape (unchanged/removed/added lines with counts), which no sibling (text_stats, text_extract, summarize) shares. It does not explicitly contrast itself with any sibling tool, but the operation is distinctive enough that confusion is unlikely.

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?

Gives clear context for when to reach for it: 'Use to see what changed between two versions of a document, config or prompt.' It stops short of naming alternatives or exclusions (e.g. when a full text comparison isn't appropriate), so it's clear context without routing guidance.

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