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

Annotations already convey it is a mutation (readOnlyHint=false, destructiveHint=false). The description adds real behavioral context beyond those flags: the hard limit of 200 items per call, the session-scoped validity of IDs ('IDs só de list_transactions/search deste turno'), and the input flexibility of accepting a single object instead of an array. It does not disclose failure semantics (partial vs. atomic) or auth requirements, but the added operational constraints are substantial and genuinely useful.

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?

Five dense sentences, zero filler. The core action is front-loaded, and every subsequent sentence adds a distinct piece of information: item structure, alias options, ID provenance constraint, accepted input shapes, and sibling routing. Nothing is repeated from the schema or 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 moderate-complexity batch mutation with no output schema, the description covers all invocation-critical aspects: what it does, item structure, aliases, limits, ID provenance, and the preferred alternative. The only gap is failure behavior (whether a bad item fails the whole batch), which is a minor omission given the annotations already establish the safety profile.

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%, so the description carries the full burden for the sole parameter `updates` — and it delivers. It explains the required composition of each item (one ID + one description), the field aliases (transaction_id/id, transaction_uuid/uuid, description/new_description), the OR relationship between ID types, and the cardinality limits (max 200, or a single object). Without this text, an agent could not correctly construct a request from the bare 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 opens with a specific verb and resource: 'Substitui a descrição de VÁRIAS transações em uma chamada (máx. 200)' — replaces descriptions of MULTIPLE transactions in one call. It immediately distinguishes itself from the singular sibling (organizze_update_transaction) by emphasizing multiple-per-call, and from mass_update_transactions by scoping to per-item updates. The function of the tool is unambiguous.

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?

Explicitly routes to the alternative: 'Se a mesma descrição/regra vale para todas, prefira mass_update_transactions' — naming the sibling and the exact condition that should select it. It also states a hard prerequisite/constraint: IDs are valid only if sourced from list_transactions/search of the current turn, which tells the agent when invocation will fail. This is explicit when/when-not guidance.

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