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

Annotations already cover read-only/idempotent/closed-world, but the description adds substantial context the annotations cannot: pricing basis (median sale vs. lowest asking order for headline_total_value), units (USD cents), ordering (oldest first), the coverage constraint ('only inventories that have been looked up have a series'), and that it reads stored data, never live Steam, with no key needed.

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 purpose, then the pricing-basis caveat, the stored-data guarantee, and finally the sibling routing. Dense but nearly every clause carries information; the rust.wiki chart reference and parentheticals add minor bulk but aid recognition.

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?

There is no output schema, so the description carries the burden of describing returns — and it does, naming `values` (USD cents, oldest first), `headline_total_value`, and `headline_checked_at` with their differing price bases. Combined with the coverage constraint, an agent has everything needed to call and interpret it.

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 range values, custom start/end dates, and interval auto-downsampling. The description only echoes this at a high level ('any range, daily/weekly/monthly') and adds nothing about parameter interaction beyond what the schema states, so the baseline 3 applies.

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 resource and metric ('the inventory's value over time... re-priced at each day's Steam SALE price') and explicitly distinguishes itself from get_inventory's 'thinned one-year series'. An agent can tell this apart from get_inventory, get_inventory_valuation and get_inventory_snapshot without opening any schema.

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 an explicit selection rule ('Use this for the value-over-time graph's data points... get_inventory only carries a thinned one-year series') and a prerequisite recovery path ('Look the inventory up with get_inventory first if it returns found=false'). Both when-to-use and the alternative are named.

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