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

With no annotations, the description carries the full burden; it does disclose real behavioral facts — PRO/subscriber gating, half-hourly granularity, and the today/tomorrow time horizon — which are genuinely useful. It does not say whether tomorrow's prices are always available, what the units are, whether results are ordered, or anything about rate limits or pagination.

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?

A single front-loaded sentence with no filler; the tier marker, resource, granularity, time window, and scoping key all appear immediately. Nothing in it is redundant with the schema.

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?

The tool is simple and read-only, and the description covers data type, granularity, time range, and region scoping. But with no output schema and no annotations, an agent still lacks the return shape (list of slots with timestamps and prices?), units, and ordering, which is a meaningful gap for the primary data-fetch tool.

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 both parameters are already documented in the schema, and the description only echoes that the postcode determines the region. No additional syntax, format, or token-handling guidance is added beyond the schema baseline.

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 resource (half-hourly import prices), scope (all published, today/tomorrow, postcode region), which lets an agent distinguish it from siblings like cheapest_slots or daily_average that return subsets or aggregates. Sibling names are never mentioned explicitly, so the contrast is inferred from 'All published' rather than stated.

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: 'All published' suggests using this when the full price curve is needed rather than a filtered/derived view, but the description never says when to prefer cheapest_slots, best_window, or daily_average. The 'PRO.' prefix hints at an entitlement gate but does not spell out what happens without it.

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