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

Annotations already declare readOnlyHint=true, so safety is covered. The description adds genuinely new behavioral context: that the call is FREE (no billing/quota impact) and requires no arguments, plus that it doubles as a connectivity probe.

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 terse fragments with zero filler, and the core purpose is front-loaded. The telegraphic style is efficient, though the fragmentary phrasing is slightly abrupt even for a trivial tool.

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-arg, read-only lookup with no output schema, naming the returned fields and the free/connectivity nature covers what an agent needs. Only auth requirements and the distinction from mcg_quote are unaddressed.

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 is 4. The description usefully notes 'no arguments' and lists the fields the caller can expect back, which partially compensates for the absence of an output 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 resource ('the public rate card') and enumerates the values it exposes (token_usd, overheads, rate_card_version). It is distinguishable from most siblings, though it does not explicitly contrast with mcg_quote, the other pricing-related tool.

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 dual-use hint ('also a connectivity check') and 'FREE, no arguments' imply when to reach for it, but there is no explicit when-to-use vs mcg_quote or statement of prerequisites/preconditions. Usage is implied rather than stated.

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