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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds only that the returned history is at daily granularity, and says nothing about pagination, result size at the 400-day maximum, or what a daily record contains.

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?

One front-loaded sentence with the verb and resource first and no wasted preamble. The 'rather than guessed' rationale is the only slightly soft phrase, but it does justify why an agent would call this instead of estimating.

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 and only a third of parameters documented, the definition leaves the return shape undefined - no fields per day, no price unit or currency, no behaviour for an unknown commodity or district. For a data-retrieval tool that an agent must interpret, this is thin.

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?

Only 'days' is documented in the schema (33% coverage, with default and max already stated there). The description partly compensates by making the cardinality explicit - one commodity, one district - but it never says whether those values are names, codes, or IDs, which is the real gap.

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 sentence names a specific verb and resource ('Return the daily price history') and constrains scope to one commodity in one district. That single-district framing implicitly separates it from compare_districts, but no sibling is ever named, so differentiation relies on inference.

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?

The trailing clause ('so the change over time can be stated precisely rather than guessed') hints at a use case, but there is no statement of when to prefer this over get_market_price (current price) or compare_districts. The agent must guess which sibling to call.

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