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

No annotations exist, so the description carries the full burden. It does add genuinely useful behavioral context that structured fields do not: the call costs $0.001 USDC via x402, which matters for agent budgeting. However, it says nothing about output units (degrees? true vs. magnetic north? km vs. miles) or the deterministic, stateless nature of the computation.

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 sentence plus a bracketed price tag, with the resource and outputs front-loaded and zero 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 two-parameter, stateless computation with no output schema, the description covers the inputs, both outputs, and the price. The only material gap is output units and coordinate format, which an agent would have to discover empirically.

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% (lat/lng are documented as Latitude/Longitude), so the schema does the heavy lifting and the baseline is 3. The description's 'from any lat/lng' adds no format guidance — notably it does not clarify the string-typed coordinates, expected decimal-degree format, or valid ranges.

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 states a specific computational result — compass bearing to the Kaaba plus great-circle distance — from a given lat/lng. No sibling in the set computes this, so an agent can distinguish it from halal_city or prayer_times on the description alone.

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 implied by the single-purpose nature of the tool (you have coordinates and need a bearing), but the description states no explicit when-to-use condition, no prerequisites, and no alternatives or exclusions.

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