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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the agent knows this is a safe read operation. The description adds that it can return a whole chapter or a single verse depending on the optional verse parameter, but this is also implied by the schema. It does not add significant behavioral context beyond that, so a baseline score of 3 is appropriate.

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 exactly two sentences. The first sentence states the core functionality, and the second gives an explicit alternative. There is no wasted wording, and the most important information is front-loaded.

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?

Given the tool's simplicity, full schema coverage, and read-only annotations, the description provides enough context for an agent to invoke the tool correctly. However, it does not mention the return format (e.g., the text of the verse/chapter), and there is no output schema to compensate. This is a minor gap, so a 4 is justified.

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%: both 'chapter' and 'verse' have descriptive text (e.g., 'Chapter (surah) number, 1-114' and 'Verse number within the chapter. Omit for the whole chapter'). The description does not add additional parameter semantics, but the baseline of 3 is correct because the schema fully covers the parameters.

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 uses the specific verb 'look up' and clearly states the resource: 'a chapter of the Quran, or one verse within it, by number.' It also distinguishes itself from sibling prayer_search by specifying the alternative use case.

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 explicitly states when to use this tool (when naming a chapter/verse reference) and when to use an alternative: 'Use prayer_search to ask a question instead of naming a reference.' This provides clear when-to-use and when-not-to-use guidance.

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