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

Annotations only flag destructiveHint/idempotentHint generically; the description explains the actual destructive mechanic (each list replaces that list as a whole, an omitted list keeps its value), the permission prerequisite checked via list_organisations, and that derived values (tax, levy, amount due) are computed server-side. It also discloses the return shape, which matters 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 change scope, then replacement semantics, then permission and return behavior. Every sentence carries information, though it is a dense multi-clause paragraph rather than cleanly separated statements.

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?

Covers mutation semantics, partial-update rules, authorization preconditions, and the return value (plan as get_savings_plan shows it), compensating for the absence of an output schema. Nothing an agent needs to invoke this correctly appears 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 schema already documents each field, setting a baseline of 3. The description adds semantics not in the schema: the replace-as-a-whole behavior of each list parameter and the instruction to omit lists that should not change, which materially affects how arguments must be constructed.

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 and resource ('Changes the savings plan of one New Zealand tax year') and enumerates exactly what fields can change (opening balance, monthly planned/saved amounts, IRD/ACC payments). It is clearly distinguishable from get_savings_plan (read) and copy_savings_plan_from_previous_year (copy).

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 tells the agent to start from get_savings_plan and include entries that should stay, names the sibling to read first, and gives an exclusion ('Only for an organisation where this connection may add and change records'). It also constrains input scope ('Send only what the person tells you').

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