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

With no annotations, the description does useful work: it discloses the paid-call model ($0.005 USDC via x402) and that nisab thresholds are fetched live rather than hard-coded. It does not explain how gram holdings are converted into the requested currency, whether missing fields are treated as zero, or whether the 2.5% rate is ever configurable — gaps an agent would want closed for a mutation-free but cost-bearing call.

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?

A single dense sentence with no wasted clauses; the paid-call cost is front-loaded so an agent sees it before deciding to invoke. The midpoint is slightly overloaded by the long asset enumeration, but it stays readable.

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 an 11-parameter tool with no output schema, the description names the three return values (nisab threshold, net worth, amount due) and the live-price dependency, which is the core of what an agent needs. Remaining gaps — default behavior for omitted fields and FX conversion for gram inputs — are modest but real.

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%, so every one of the 11 fields is already documented in the schema. The description's enumeration of cash, gold/silver grams, investments, crypto, inventory, receivables and debts restates those fields and adds only that the calculation works 'in any major currency' — baseline 3.

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+resource ('Zakat calculator') plus the exact outputs it produces: live gold/silver nisab thresholds, zakatable net worth, and the 2.5% amount due. That is enough to distinguish it from every sibling in the list (islamic_calendar, halal_*, screener), none of which compute anything.

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 only implied by the domain: an agent can infer you call this when a user asks how much zakat is owed. There is no explicit when-to-use framing, no mention of prerequisites (e.g. needing live metal prices or a currency), and no statement about what happens if called with no arguments, which matters for an all-optional schema.

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