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

Annotations already signal that this is not read-only, not idempotent, and not destructive, and the description adds meaningful behavioral context: this is a partial update, automatic transactions only allow certain mutable fields, and IDs must come from prior read operations. It does not explain every edge case, such as update_recurrence behavior, but it covers the most important operational constraints.

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 compact and front-loaded with the core purpose, followed by high-value constraints. Every sentence adds operational knowledge, and the bulk-support note is clearly separated. There is no filler or repetition of information already present in the annotations or schema.

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 12-parameter mutation tool with no output schema and no parameter descriptions, the description does a solid job covering the most critical pitfalls: ID provenance, naming preferences, automatic-transaction field restrictions, and bulk routing. It is not fully complete because update_recurrence semantics and response behavior are left unspecified, but the key decisions needed to invoke the tool correctly are addressed.

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 must compensate, and it does partially: it tells the agent that account and category should be names, that transaction_id and transaction_uuid must be copied from existing tools, and that transaction_ids enables bulk. However, several parameters such as date, paid, amount, tags, and update_recurrence are not individually explained beyond their schema names, so the compensation is incomplete.

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: "Atualiza uma transação existente" (updates an existing transaction), and clarifies the scope by saying only the fields to change should be sent. It also explicitly distinguishes itself from mass_update_transactions, so an agent can tell it apart from an important sibling without opening the schema.

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 gives explicit usage rules: prefer account/category names over invented IDs, copy transaction_id/uuid from list/search/get operations, never invent or sequence IDs, and use mass_update_transactions for multiple rows. It also names the alternative tool explicitly, which is strong guidance for when to use this one.

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