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

No annotations exist, so the description carries the full burden. It usefully discloses a per-call cost ($0.01, USDC on Base), which is real behavioral context an agent needs, but it omits whether the call is side-effect free/idempotent and how edge cases (zero, negatives, very large numbers) behave.

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 with the core action and an example, then use cases, return, and pricing. 'Returns the number spelled in Persian words' partially restates the opening sentence, a small redundancy.

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 single-parameter, no-output-schema tool this covers input, output, intended contexts, and cost. The main gap is sibling differentiation from fa_amountToWords, which matters given the overlap in stated use cases.

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 coverage is 100% for the single parameter, so baseline is 3. The description's example ('1234 as هزار و دویست و سی و چهار') demonstrates both the accepted input form and the resulting output string, adding meaning beyond the schema's 'integer, string digits, commas or Persian digits'.

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 (convert an integer into Persian words) with a concrete worked example, so the transformation is unambiguous. It does not differentiate from the near-identical sibling fa_amountToWords, which an agent could easily pick instead.

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 lists contexts (invoices, cheque amounts, legal/official forms, display), which gives implied usage. However, those are exactly the scenarios fa_amountToWords would also serve, and the description never says when to prefer one over the other or when not to use this tool.

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