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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It names a constant but does not state the value, the units (m/s² vs m³/s²), or the return format. With no output schema and no annotations, the agent cannot know what invoking this tool will actually yield.

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?

The description is only five words, so there is no wasted prose, but the leading 'Earth Gravity:' merely restates the tool name, and the remaining fragment is under-specified. It is terse rather than economical — it leaves out units and value information that would cost only a few more words.

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?

Despite the tool's low complexity (zero params), the description is not complete enough. It does not specify units or which gravitational quantity is returned, there is no output schema to compensate, and the ambiguity between g and GM is material given the closely named sibling x402-gravitational-constant. A single sentence stating the value and units would close the gap.

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?

The tool has zero parameters and an empty input schema, so there is nothing for the description to clarify. Per the rubric, 0 params earns a baseline of 4; the description's naming of the constant confirms no input is required.

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?

The description identifies a specific resource, 'Earth gravitational constant', which is a named physical quantity, so the agent knows roughly what to expect. However, it lacks any verb ('returns', 'provides', 'looks up') and does not distinguish itself from the closely related sibling x402-gravitational-constant (the universal constant G) or from x402-earth-mass / x402-earth-radius. The phrase is also slightly ambiguous between standard surface gravity g (9.81 m/s²) and the geocentric gravitational constant GM.

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?

There is no guidance whatsoever about when to use this tool versus alternatives. The sibling list contains many physics constants and gravity-related tools (x402-gravitational-constant, x402-gravitational-force, x402-acceleration), and nothing in the description tells an agent how to pick among them.

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