Update Transaction

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

Annotations already declare readOnlyHint=false, idempotentHint=true, destructiveHint=false, so the safety profile is covered. The description adds genuinely new behavioral context beyond them: patch semantics for omitted fields and the permanent restriction that YNAB cannot re-split an already-split transaction. It does not mention auth/permission requirements or error behavior on an invalid transactionId.

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?

Two sentences, no filler, and the most load-bearing fact (only transactionId required; only send what you want changed) is front-loaded ahead of the edge case about splitting.

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 mutation tool whose annotations already carry the safety profile and whose schema is fully documented, this covers the mutation model, the split workflow and its key limitation. Minor gaps remain around permissions and failure modes on a bad transactionId, but nothing essential to invoking it correctly is missing.

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 the baseline is 3 and the schema already documents all 14 parameters including the split sub-shape. The description adds a usage rule the schema does not state plainly - supply only the fields you intend to change, and omit categoryId when passing subtransactions - which meaningfully affects how parameters are passed.

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+resource ("Updates an existing transaction") and immediately clarifies the patch semantics, so an agent understands this is a partial mutation rather than a replace. It never names the sibling it is distinguished from (ynab_create_transaction, ynab_delete_transaction, ynab_approve_transaction), 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?

"All fields except transactionId are optional - only provide fields you want to change" gives clear when-to-use guidance for a patch tool, and the subtransactions sentence states the condition and the one hard exclusion (cannot re-split an already-split transaction). No explicit routing to alternative siblings (e.g. approve vs update), which keeps it below 5.

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