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

Annotations already declare readOnlyHint=true, but the description adds critical behavioral context beyond that: it warns that guessed slugs 'routinely fail validation' and explains the naming pattern is inconsistent ('en-sahih-international' vs 'clearquran-with-tafsir'). It also discloses that Arabic is unsupported and that this tool must not be followed by get_translation_text, which are meaningful behavioral traits.

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 longer than typical but each section earns its place: purpose, usage exclusions, slug handling, and format constraints. It is front-loaded with the essential purpose in the first sentence. Slight redundancy exists (e.g., Arabic unsupported is mentioned both in description and schema), but overall the structure is logical and well-organized.

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 tool with one parameter object containing nested fields, several sibling alternatives, and additional prerequisites (like lookup_translations), the description covers all necessary context. It explains when to choose this tool over get_translation_text, how to handle slugs, what constraints apply to languages/translations, and defines the final-call behavior. An output schema exists, so the lack of return-value details is acceptable.

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?

While the schema covers 100% of parameters, the description adds substantial meaning beyond schema descriptions. It clarifies ayah key format with examples, specifies that language codes must be ISO 639-1 and not language names, and provides concrete slug examples while explaining the need to resolve slugs via lookup_translations. This directly addresses common parameter misuse.

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 the tool's purpose: 'DEFAULT tool for user-facing translation display' and specifies it is for 'ANY user-facing request to show/see translations of a Quran ayah'. It explicitly distinguishes itself from the sibling tool get_translation_text by noting this is the FINAL tool call for display requests, making the purpose unambiguous.

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 provides explicit when-to-use and when-not-to-use guidance: use for any user-facing translation display, but skip and use get_translation_text when plain text/raw text is requested or when the result will be piped to another tool. It also directs to lookup_translations for slug resolution, naming a specific alternative and the exact conditions under which to use it.

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