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

Beyond the neutral annotations, the description discloses meaningful behavior: it returns 'Updated budget details,' rollover is only applicable to monthly budgets, and passing an empty name clears the custom name and falls back to the category name. This gives an agent useful insight into edge-case behavior.

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 front-loaded with the action and uses a clear Args/Returns structure. Every line adds useful parameter information; only the 'Phase 92' note is slightly tangential, but it does not prevent the definition from being compact.

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 simple partial-update tool with no output schema, the description covers the required budget_id, all optional fields, valid values, and the return value. It could note whether at least one optional field is required and clarify how period changes interact with rollover, but nothing essential is missing for a straightforward call.

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%, but the description documents all five parameters with purpose, optionality, valid values for period, and behavioral notes for rollover and name. This fully compensates for the empty schema and gives the agent semantics the schema lacks.

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 'Update an existing budget,' which names a specific verb and resource, and the word 'existing' distinguishes it from create_budget and delete_budget. It is clear but does not explicitly call out sibling tools or state when not to use it.

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?

No when-to-use guidance is provided beyond the verb itself. The description does not direct an agent toward create_budget for new budgets, list_budgets for finding budget IDs, or delete_budget for removals, and it does not state prerequisites for calling the tool.

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