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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so safety is covered. The description adds genuinely useful non-schema context: the operation consumes 1 credit, and the response includes total base points, letter count, and per-letter values. It does not discuss failure behavior for invalid characters or unsupported languages, so a 3 fits.

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 and short, but the opening wastes space by repeating the tool name verbatim ('Scrabble Word Scorer: Scrabble Word Scorer calculates...'). The remaining two sentences are efficient, carrying purpose, scope, return contents, and cost.

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?

For a simple two-parameter, single-purpose tool with an output schema that already documents return values, the description covers purpose, language scope, and credit cost. The main residual gap is the unnamed set of supported languages, which matters because the schema provides no enum to constrain them.

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%, so both parameters are documented and the baseline is 3. The phrase 'five languages' adds a small amount of meaning beyond the schema's unconstrained 'Scrabble language variant' (there is no enum), but the five variants are never named, so the agent still cannot know which values are accepted.

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 ('calculates the official Scrabble score for any word') plus scope ('across five languages'), which is unambiguous and distinguishable from neighboring word tools like VowelCounter or WordLexiconAnalyzer. It stops short of naming or contrasting any sibling explicitly, so it lands at 4 rather than 5.

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?

There is no when-to-use or when-not-to-use guidance, no mention of alternatives for related tasks (e.g. scoring vs. validating vs. analyzing words), and no prerequisites. Usage is only inferable from the tool's name and the word 'score', which is the definition of no explicit guidance.

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