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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so safety is covered. The description still adds useful non-schema context: that this is a received-payment accounting record and that payment processing is not supported. That said, the 'ProcessPayment must be omitted or false' clause references a parameter that does not exist in this schema, which is confusing rather than informative.

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?

It is short, but the front-loaded purpose sentence is tangled ('when no search or write answer already holds it') and the trailing ProcessPayment sentence consumes space on a parameter that does not exist in this tool's schema. Two of three sentences carry real weight; the middle one is somewhat redundant with the annotations.

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 read tool with no output schema, the description covers what the tool returns conceptually (a received customer payment record), how to locate it (by Id), and when to prefer it over search. The missing pieces — return shape and error behavior on an unknown Id — are minor given the readOnly annotations.

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% with only two parameters (id, company), both documented in the schema, so the baseline is 3. The description adds no format or syntax detail for 'id' or the company selector, and its only parameter-adjacent remark (ProcessPayment) points at a field that isn't 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?

States a specific verb and resource ('Get a single payment ... by Id') and clarifies the domain object as 'an accounting record of a customer payment already received', which separates it from the payment-processing concept. It doesn't explicitly distinguish itself from other sibling single-get tools like get_bill_payment or get_tax_payment, so it stops short of a 5.

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?

Provides a real routing condition: use it 'when no search or write answer already holds it', implying the search_* tools are preferred when a list result suffices. It never names search_payments explicitly and gives no explicit exclusions for the other payment-family getters, so it's clear context but not a complete when/when-not rule.

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