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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered; the description adds the useful 'No key needed' auth note and describes the payload contents. It does not say what happens when the date has no snapshot or how to discover valid dates (only implicitly via the schema's reference to the snapshots endpoint).

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 resource, then payload, then use case, then auth. Mostly efficient, though the opening sentence largely restates the title 'One saved daily snapshot' rather than adding information.

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?

With no output schema, the description carries the burden of describing return contents and does so (items, quantity, day's price, total value, item count). Missing only edge-case behavior for a nonexistent date; for a 2-param read tool this is largely complete.

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% — both date (ISO YYYY-MM-DD, sourced from the snapshots listing) and steamid (17-digit SteamID64) are fully documented in the schema. The description adds only the 'that day's price' framing for date; it says nothing about steamid, so 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?

The description states a specific resource (a single saved daily inventory snapshot) and enumerates its contents — items, quantities, that day's price, total value, item count. It's clear what is returned, but it never names the sibling it isn't (list_inventory_snapshots for enumerating dates, get_inventory for the current state), so sibling differentiation is left implicit.

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?

'Useful for "what was this worth last month" comparisons' implies a historical-comparison use case but gives no explicit when-not or routing rule to list_inventory_snapshots (to find dates) or get_inventory (for current values). The usage is inferable but not spelled out.

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