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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered; the description adds genuinely new context: it enumerates the return payload (adjusted price, per-index ratio and effect, formula) and discloses a base-date lookback limit that is not in the annotations. The 'rest is fixed' convention is a useful behavioral detail, though rate limits or failure modes are not covered.

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 sentences, front-loaded with the operation, then inputs, then outputs, then constraints. No filler; every clause carries 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?

For a read-only calculator with no output schema, the description supplies the return shape and a key access constraint, which is most of what an agent needs. It stops short of clarifying the shortcut-vs-components input choice, the only remaining gap.

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 71%, so most parameters are documented structurally. The description reinforces base price/date and the weights concept and adds the 'rest is fixed' meaning, but it never disambiguates the top-level code/weight shortcut from the components array, which is the one genuinely ambiguous part of the schema.

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 ('Recalculate an index-linked contract price') and clarifies the inputs (base price, base date, indices, weights) and the fixed remainder. This distinguishes it from calculation-adjacent siblings like estimate_packaging_price and explain_price_move, though it does not name any sibling explicitly.

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 plan-tier note ('Essential plan (base dates up to 3 months back), Professional (24 months)') gives a real precondition, but there is no explicit statement of when to choose this over explain_price_move or get_index_history. Usage is implied rather than spelled out.

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