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

Annotations already establish a safe read (readOnlyHint=true, destructiveHint=false, openWorldHint=false), and the description adds genuinely new behavioral context: the card charge and ledger credit occur asynchronously and amount_usd is null while pending. That explains a non-obvious return-state without repeating the annotation.

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?

Three tight sentences: purpose and key first, return shape second, the negative disambiguation last. Nothing is redundant and the most useful 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?

With no output schema, the description inventories the return fields (status, settled, amount_usd, settled_at, balance_usd, is_exhausted) and explains the pending-state null, so an agent knows what to expect. Nothing material is missing for a single-parameter read tool.

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% and the schema already defines reference_id with an example and a pointer to get_credit_transactions, so the description adds little beyond narrowing scope to 'one existing' payment. Baseline 3 applies when the schema carries the parameter detail.

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 ('Read settlement status for one existing credit payment') plus the keying parameter, which cleanly separates it from get_credit_transactions and get_credit_balance. An agent can identify the right tool without opening the 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?

Scoping is clear ('one existing credit payment by reference_id') and it explicitly rules out a misuse ('This tool does not initiate a purchase'). It points to get_credit_transactions as the source of the reference, but gives no positive guidance on which tool to use when a purchase does need to be initiated.

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