switch_book

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

Beyond the annotations, the description reveals the critical stateful behavior: all subsequent tool calls and logs operate on the newly-selected book until the next switch. This is valuable contextual information not derivable from readOnlyHint, idempotentHint, or destructiveHint.

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, front-loaded with the action, and each sentence adds necessary context without redundancy. The stateful consequence and availability condition are both conveyed efficiently.

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 state-switching tool, the description covers the essential context: what the tool does, when it is available, and how the change affects subsequent operations. The output schema exists, and the input schema handles parameter specifics, so nothing critical is 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%, and the tool description itself adds no parameter details. The schema already fully documents the matching semantics and uniqueness requirement, so the baseline of 3 is appropriate.

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 uses a specific verb ('Switch') and resource ('active GnuCash book'), immediately distinguishing it from all sibling operations. It also clarifies the multi-book-session scope, leaving no ambiguity about what the tool does.

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?

It explicitly limits usage to multi-book sessions and states when the tool is present ('Only present when GNUCASH_BOOK_PATH lists 2+ books'). It clearly implies that this should be called before other tools when targeting a different book, though it does not name alternatives or explicit when-not-to-use cases.

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