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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), but the description adds real behavioral context: sampling granularity (every point ≤3mo, weekly closes beyond), plan-dependent depth caps, and the free-tier cutoff. That is meaningful disclosure beyond the structured fields.

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 and packs resolution rules, depth limits, and free-tier cutoff into a compact two-clause structure. Dense but each clause carries information; slightly crammed with semicolons rather than wasteful.

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 correctly describes the return shape (one value per date plus the change between points) and the sampling behavior. Only minor gaps remain, such as response format and pagination for longer spans.

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 baseline is 3, but the description earns extra by spelling out the plan-to-depth mapping (observer/essential 3mo, professional/intelligence 24mo) that the schema only alludes to as 'Capped to the caller's plan depth'.

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 ('Price history for any PackIndex code') and adds resolution/scope detail (one value per date, L0-L3 coverage). It clearly implies historical data versus live/forecast siblings but never names an alternative, so it stops short of full sibling differentiation.

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?

Usage is only implied through the plan-depth note and 'free history ends 12 weeks ago', which tell the caller about limits but not when to pick this over get_live_index or get_index_forecast. No explicit when-to-use or when-not-to-use guidance is given.

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