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

No annotations exist, so the description carries the burden and does reasonably well: it discloses the index base (100 at series start), that the result is an aggregate not a product, the default scope ('all', whole catalogue), and how to judge freshness via lastComputedAt. It doesn't explicitly state read-only/no-side-effects, but the framing strongly implies a pure read.

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?

Three short sentences, all load-bearing: purpose first, usage/alternative second, freshness hint third. No filler or repetition of the title.

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 single-optional-param read tool with no output schema, the description covers what the data means (index, base 100, category granularity) and freshness. It could say slightly more about the response shape (e.g. the series/points structure) since no output schema exists, but 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 coverage is 100%, so the parameter is already fully documented, including the default and availableCategories. The description only mildly reinforces the category-level semantics ('describes a category, not an individual product') and adds no syntax or format detail beyond the schema. 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 verb and resource (month-by-month price movement for a category of UK components) plus the index convention (base 100 at series start). It explicitly distinguishes itself from get_price_verdict as category-level vs single-product, but never mentions the sibling get_price_history, leaving a plausible overlap unresolved.

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 a concrete use case ('answer whether prices in a category are rising or falling') and an explicit alternative for the individual-product case ('for one product use get_price_verdict'). No exclusion against get_price_history, which is the one remaining routing ambiguity.

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