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

Annotations already declare read-only, idempotent, open-world, non-destructive behavior, so the safety profile is covered. The description adds genuinely new behavioral context beyond annotations: the cost model (free within daily allowance, then $0.002 USDC per call via x402), which matters for agent budgeting. It does not add rate limits or return shape, but an output schema exists.

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?

Two short sentences with the purpose and sibling routing front-loaded, followed by the cost note. Nothing is redundant or padded.

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 two-parameter, read-only list tool with an output schema and full annotation coverage, the description supplies everything an agent needs to invoke it correctly: scope, sibling routing, and cost. Only minor detail (e.g., ordering or volume of returned notices) is absent, which the output schema likely covers.

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 description coverage is 100%, so both 'from' and 'to' are already documented in the schema, including the ISO example. The description only restates the time-window concept without adding format or boundary semantics, so the baseline 3 is appropriate.

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 ('outage and unavailability messages') and the scope ('published between two times'), and explicitly distinguishes itself from the singular sibling by noting that individual records are fetched with 'outage'. An agent can tell it apart from gb-electricity__outage without opening either schema.

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?

Clearly frames the use case (messages in a time window) and routes to the alternative ('fetch each with outage') for per-id retrieval. No explicit exclusions or preconditions are given, but the selection context is clear.

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