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

Adds a lot beyond the annotations: one entry per month dated its last day, continuity from the last booked month, locked-period refusal with catch_up fallback, reversal semantics for undo_after, and pricing ($0.01 per call, nothing if it fails). The only tension is that 'running it again books nothing twice' reads as idempotent while idempotentHint=false, but that hint reflects the undo/catch_up modes rather than a real contradiction.

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 primary action and default, and no sentence is filler. It is one long dense run-on with several nested clauses (catch_up, undo_after, pricing), which costs some readability.

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?

No output schema and no annotation detail on effects, yet the description covers what gets booked, how repeats behave, what gets refused, fallbacks, reversal scope and cost. An agent has everything needed to call it correctly.

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 coverage is 75%, and the prose adds meaning the schema lacks: through defaults to last month end, asset scopes undo to one asset versus all, catch_up redirects locked months to the first open month, and undo_after reverses months after a date. All four parameters gain semantics beyond their bare schema entries.

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: book depreciation for every registered asset through a month's end, with a concrete default (end of last month) and a named analog (Xero's run depreciation). It is clearly distinct from books_save_asset, books_dispose_asset and books_close_year even though it never names them.

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 strong when-conditions: run for a month end, use catch_up when the period is locked, use undo_after before changing an asset's cost, life or method, and running again is safe. It stops short of naming sibling tools or stating when not to depreciate at all, so it stops at 4.

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