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

Annotations already declare the operation is a non-readOnly, non-idempotent, non-destructive write, so the bar is lower. The description goes well beyond them: it discloses the side effect on the goal's amount, the automatic month-selection behavior, and the exact return value ('the plans it replaced (before)') for undo — valuable since there is no output schema.

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?

Front-loaded with the core action, then unit/format rules, then return value. Three dense sentences carry a lot of information without filler, though the format details could be tighter and the sentence order slightly buries the undo guidance.

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 two-parameter mutation with no output schema, the description covers the side effects, return shape, currency units, and month semantics. Remaining gaps are the unspecified 'id'/'categoryId' meaning and explicit non-idempotent behavior, which are minor against the otherwise complete picture.

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 carry parameter meaning. It does explain 'amount' precisely (integer minor units, 45000 = 450.00) and the date/month format, but says nothing about the required 'id' parameter (presumably a goal id) or the 'categoryId' field, leaving half the semantics undocumented.

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 with its effect: it lowers categories' plans by given amounts and adds the total to the goal's monthly amount. This is clear enough to distinguish it from set_budget/update_goal, though it never names those siblings explicitly as the lower-level alternative. A reader understands what the tool does, but the phrasing is dense.

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?

Gives implicit usage context by naming set_budget and update_goal as the tools to reverse the operation, and by specifying the 'first budget month that still gets money in' selection rule. However, it never states when to prefer this over set_budget/update_goal for the forward operation, nor any preconditions or exclusions.

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