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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description still adds value beyond them: it guarantees the output is always ASCII, names what is dropped (macrons, dotted ġ/ċ) and folded (þ/ð, æ, ƿ, œ), and rules out dictionary lookup or network 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 short sentences with the transform rule front-loaded and the constraint ('always ASCII') trailing; every clause earns its place. Minor waste from repeating the schema's own examples in the parenthetical.

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?

An output schema exists, so return values need not be explained, and the annotations carry the safety/idempotency profile. The description covers what the transform does, which characters change, the direction of the mapping, and the constraints, leaving nothing an agent needs in order to invoke it 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?

With one parameter at 100% schema description coverage, the baseline is 3. The description largely restates the schema text (same þing→thing, wæter→waeter examples, same letter foldings) rather than adding syntax or format meaning the schema lacks.

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 and resource ('Reduce Old English orthography to its primary ASCII spelling') and the worked examples (þing→thing, wæter→waeter) fix the direction of the transform, so an agent can tell it apart from the inverse sibling anglo_deromanize without opening either 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?

Gives clear selection context: it is for 'an ASCII-keyboard downstream' and is a 'pure local transform: no dictionary lookup, no network', which implicitly steers lookup needs toward the search/deromanize siblings. It stops short of naming an explicit alternative or a when-not condition, so it falls just under the top band.

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