Merge payees

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

Annotations already declare destructiveHint=true, idempotentHint=false, and openWorldHint=true, so the irrevocability is partially covered. The description still adds specifics annotations cannot: that it voids transfers when target has a transferAccountId and that merged payees are removed. That is real added context beyond annotations, but it repeats the irreversibility the annotation already encodes, so a 3 is fitting.

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 irreversible warning is front-loaded before the operational details, and three sentences each carry distinct content. Slightly dense in the middle, but no filler sentences.

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 destructive, non-idempotent, open-world operation with no output schema, the description covers preconditions, in-place effects, and failure modes. It does not describe the return value, but there is no output schema to lean on and the tool's effects are the important information here.

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 baseline is 3. The description adds the non-obvious distinction that ids are taken, not names, which is a semantic constraint beyond the schema, and clarifies that mergeIds cease to exist and targetId is retained. Slightly above baseline.

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 (merge) and resource (payees), plus the exact transactional semantics: transactions move to target and merged payees are removed. Distinguishable from sibling find_duplicate_payees (which finds, not merges) and create_payee/update_payee.

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?

Explicit when-to-use (only when payees really are the same merchant), a hard precondition (never merge a payee with a transferAccountId), and a failure mode to avoid (near-miss names). Nothing is left to inference for an irreversible operation.

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