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

With no annotations, the description carries the full behavioral burden and offers essentially none: it does not say whether this is a partial or full replacement update, what happens to omitted fields, whether the payment record is mutable after issuance, or what permissions are required. 'Update' alone discloses nothing beyond the mutation implied by the name.

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 short, front-loaded sentence with no filler. It is efficient, though that efficiency comes partly from omitting content the agent needs.

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?

This is a six-parameter mutation tool with no annotations and no output schema, yet the description covers only the ID-based targeting. The partial-vs-full update semantics and post-call state are entirely undocumented, which is a real gap for a destructive-capable operation.

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%, so every parameter including the ID's provenance from search_payments and the YYYY-MM-DD date format is already documented. The description adds no parameter-level meaning beyond the schema, which is the baseline 3 case.

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 ('Update') and resource ('an existing payment by ID'), so the action is immediately clear. However, it does nothing to separate it from the surrounding create_payment / delete_payment / search_payments family, which the agent must infer from names alone.

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?

There is no guidance on when to update versus create or delete a payment, nor any prerequisite such as needing a payment ID obtained from search_payments (that hint lives only in the schema). The agent is left to infer usage entirely.

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