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

Goes well beyond the annotations by disclosing the 2,000-character input cap, deterministic 'pure code' behavior, unsupported-script handling, and an explicit price model ($0.002 USDC per successful call via x402 on Base/Solana/Arc, failures free) — payment and billing details an agent cannot infer from schema or annotations. There is a mild tension with openWorldHint=true since the tool is a fixed lookup table with no external calls, but this is an annotation looseness rather than a description contradiction.

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?

Four compact sentences, front-loaded with the two capabilities, then coverage, then edge-case behavior, then limits and pricing. No filler and no repetition of schema text.

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 an output schema present, the description needn't explain return values, and it isn't required to — the 'unconverted' mention even hints at the return shape. Annotations cover safety, schema covers parameters, and the description covers limits, fallback behavior, and cost, leaving nothing material unstated.

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 already 100%, so the baseline is 3; the description adds value by explaining what 'mode' means in practice (ASCII vs URL slug) and reinforcing the text length limit, which is the parameter most likely to cause a failed call. Separator semantics are left entirely to 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?

Opens with a specific verb+resource ('Transliterate text to Latin ASCII') and immediately names the second capability ('make a URL slug'), which cleanly separates it from siblings like translate, encode, or the other text_* utilities. The script coverage list further pins down exactly what domain of input it handles.

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 two modes give clear usage context (ASCII normalization vs URL slug creation) and the description states the fallback rule for unlisted scripts (kept and reported in 'unconverted', not guessed), which is genuine usage guidance. It does not explicitly say when to prefer a sibling such as translate or encode instead, so it stops short of full routing guidance.

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