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

With no annotations, the description carries the burden. It discloses that the tool requires a Pro key, returns a URL to a chart image, and supports PNG/SVG/PDF. This is useful behavioral context beyond the schema, though it does not detail error handling or data source behavior.

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 three concise sentences, immediately stating the core function before supplementary details. No redundant or verbose wording.

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?

Given the simple tool signature and the presence of an output schema, the description covers the main purpose, return format, tool-specific requirements, and output formats. It lacks specifics about the chart axes or window size definitions, but these are less critical for invocation.

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?

All four parameters have full schema descriptions (100% coverage), so the baseline is 3. The description's mention of PNG/SVG/PDF duplicates the fmt parameter's schema description and adds no new parameter meaning.

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 clearly states the tool generates a range-box chart of elevation statistics (Min/Avg/Max) across three window sizes, distinguishing it from sibling tools that fetch elevation values, stats, or other chart types.

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 does not explicitly compare with sibling tools or state when to prefer this chart over other elevation tools. It mentions a Pro key requirement, but no 'use this when...' guidance, so usage context is only implicit.

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