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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds a small amount of behavioral context by noting the return preview is Markdown and structured, and that locale scope depends on whether language is supplied. It does not contradict annotations.

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?

The description is two sentences, front-loaded with the primary action and resource, and does not waste words. The only slightly vague phrase is 'bounded Markdown', but overall the definition is appropriately compact.

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 read-only lookup tool with 100% schema coverage, an output schema, and strong annotations, the description is nearly complete. It accurately captures the exact-key semantics and optional language narrowing. It would be more complete if it explicitly directed agents away from search_phrases or list_phrases, but the wording already implies that boundary.

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 the schema already documents key, project, and language in detail. The description mostly restates the language behavior ('single locale when language is provided') that the schema already covers, adding little semantic value beyond what structured fields provide.

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?

The description clearly states a specific verb ('Fetch') and a concrete resource ('translations for one exact phrase key in a MultiLocale project'). It also differentiates from siblings by emphasizing 'one exact phrase key', which excludes list_phrases and search_phrases without needing to open their definitions.

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 description conveys the intended use case: retrieving translations for a specific exact key, optionally narrowed to one locale. It does not explicitly name alternatives or say when not to use it, but the context is clear enough for an agent to select it over list/search variants.

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