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

Annotations already cover safety (readOnlyHint, idempotentHint, non-destructive, closed-world), so the bar is lower. The description adds genuinely new context beyond them: 'Free, no sign-in' discloses that no authentication or credit spend is required, and it warns that other tools may spend credits. It does not describe response shape, but the output schema covers that.

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-loads the most decision-relevant fact ('Free, no sign-in') and then packs the coverage list, credit behavior, pricing, and account connection into one efficient sentence, closing with the routing instruction. No sentence is filler.

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 zero-parameter, read-only overview tool with an existing output schema, everything an agent needs is present: what it returns, that it is free and requires no sign-in, and when to call it. Nothing material 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?

Zero parameters, so the baseline of 4 applies. The description adds nothing about parameters because there are none to describe, which is appropriate for a no-argument overview tool.

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 ('Describes Hercules') and enumerates exactly what it covers: coverage areas, per-tool credit behavior, plan and credit pricing, and account connection. This is clearly distinguishable from every sibling, which are all functional search/lookup/quote tools rather than a meta-overview.

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?

'Call it first when the user asks what Hercules can do or what it costs' gives an explicit trigger condition and ordering instruction. It stops short of naming when-not to use it (e.g., for actual property lookups, use the search/quote siblings), but the routing intent is unambiguous.

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