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

With no annotations, the description carries the full burden and does unusually well on the operational side: it discloses that the server is paid ('Auth mode: paid') and gives the exact cost and payment rails ($0.005 per call, USDC on Base via x402 or Tempo via MPP). It stops short of describing the returned string format or error behavior for invalid amounts.

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 functional sentence is buried under machine-generated marketplace boilerplate: origin URL, hostname, brand, provider aliases, family key, endpoint, four keyword lines, and three near-duplicate use cases. The leading line is an origin URL rather than the purpose, so the payload is not 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?

For a simple two-parameter tool with no output schema and no annotations, the description covers purpose, unit choice, and payment/auth requirements, which is most of what is needed. It omits the return shape, the relationship to the sibling number_to_words_fa, and any amount-format constraints.

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 0%, so the description must compensate. It names the two unit values ('toman or rial') and gives a concrete amount example ('write 125000 tomans'), which loosely mirrors the enum and clarifies the numeric scale, but it never explains whether 'amount' is interpreted in the selected unit or whether fractional/decimal values are acceptable.

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 summary states a specific verb and resource: 'Spell an amount in Persian words with the correct unit (toman or rial).' This is clear enough to distinguish it from generic word-spelling siblings, though it never names the closest sibling (number_to_words_fa) to draw the currency-vs-plain-number boundary.

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?

Usage is implied rather than prescribed: 'Use for invoices and payment memos' plus three use cases set context, but there is no when-not guidance and no pointer to the alternative (number_to_words_fa for non-currency numbers, rial_toman_convert for conversions).

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