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

Annotations show readOnlyHint=false, so the description carries the burden of explaining mutation behavior. It states that fields can be updated and that updated rule details are returned, but it does not disclose what happens when optional fields are omitted or set to null, whether a rule must exist first, or how partial updates behave. This is a meaningful gap for an update operation.

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 description is tightly structured with a clear one-sentence summary followed by an Args list and Returns line. There is no filler, and the most important 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?

The description is sufficient for a basic call, but it lacks context about null/omitted parameter semantics, whether at least one optional field is required for a meaningful update, and what the updated rule details contain. With no output schema, a bit more detail about the return value would improve completeness.

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%, and the description compensates well by explaining all four parameters in plain language: rule_id identifies the rule, description_pattern is the new substring with a length constraint, and the two account IDs are labeled as new asset and debt accounts. It adds meaning and constraints not present 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?

The description uses a specific verb and resource: 'Update the pattern or account pairing on an existing debt payment rule.' It clearly identifies what is modified and can be distinguished from sibling tools like create_debt_payment_rule, delete_debt_payment_rule, and list_debt_payment_rules.

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?

The description implies usage: it is for modifying an existing debt-payment rule, as opposed to creating or deleting one. However, it does not explicitly state when to prefer this over alternatives or mention any preconditions or exclusions, leaving the usage context mostly implicit.

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