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

Annotations already provide readOnlyHint=true, covering safety; the description adds the useful context of the percentage ranges and the swing high/low inputs. It does not, however, disclose how direction affects the levels or any edge-case behavior (e.g., high < low), so it only partially extends beyond the annotations.

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?

One concise sentence front-loads the core concept and includes the key percentage ranges without any filler. Every word contributes.

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 simple 3-parameter calculation tool with annotations, the description names the inputs and the type of output, but without an output schema it doesn't describe the return structure or how direction changes the results. This is adequate but not fully complete.

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 low (33%); only direction is described. The text maps high/low to 'swing high/low' but adds no meaning for the direction parameter, which is essential to interpret whether extensions are above or below the swing. This leaves a significant semantics gap.

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 names the exact output — retracement (0-100%) and extension (127.2-261.8%) price levels — and ties it to a swing high/low, which clearly differentiates it from sibling calculators like pivot_points. It lacks an explicit verb such as 'calculates', which keeps it just below a 5.

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 description implies when to use this tool: when Fibonacci retracement/extension levels are needed for a swing high/low. However, it does not explicitly explain when not to use it or compare it with alternatives such as pivot_points, so the guidance is only implicit.

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