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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower, but the description adds real behavioral value: it explains that esnad entries are Shamela's raw markers and 'mean nothing on their own', warns of the format, and discloses the clean has_services:false path for many books. It stops short of covering response shape or budget behavior beyond the schema's own note.

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 key purpose and the raw-marker caveat are front-loaded, and each sentence carries information (return fields, warning, follow-up routes). It is denser than strictly necessary, but nothing is filler.

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?

With no output schema, the description fully carries the burden of explaining the return shape (has_services, ayat, hadeeth, esnad, esnad_count) plus the interpretation caveat and next-step tools. An agent has everything needed to call it and act on the result.

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 baseline is 3. The description identifies book_id/page_id and reused field meanings but adds no syntax or constraint detail beyond the schema; the response_format parameter's semantics live entirely in the schema.

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 opening states a specific verb+resource: read per-page service markers (Qur'anic verses, hadith keys, isnād markers) for a (book_id, page_id). It enumerates the return fields and explicitly distinguishes itself from shamela_get_isnad, so an agent can separate it from siblings without opening a 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?

It gives explicit when-to-use (pivot from a search hit to what the page cites), names the follow-up alternatives (shamela_get_aya for aya_ids, shamela_get_books_for_hadith for hadith keys, shamela_get_isnad for resolved chains), and warns when-not (non-hadith books return has_services:false). Nothing is left to inference.

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