get_radar_image

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

Beyond the annotations (readOnly, openWorld, idempotent), the description adds critical behavioral details: update frequency ('updated roughly every 5 minutes'), return payload (PNG, area, product name, timestamps), and error behavior ('isError: true if the SMHI radar API is unreachable'). No contradiction with 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?

Three sentences cover purpose, distinction from siblings, usage caveat, return value, error behavior, and coverage. Every sentence adds new information; no filler or redundancy.

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 having no output schema, the description explains the return format and error conditions. With annotations covering safety/idempotency, the description covers the remaining essentials: update cadence, scope, and sibling differentiation. This is fully sufficient for a parameterless read-only tool.

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, so there is nothing to explain beyond what schema shows. The description explicitly notes 'Takes no parameters', which reinforces the schema. Baseline for 0 params is 4, and the description is consistent.

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 begins with a specific verb+resource: 'Get the latest Swedish precipitation radar composite', which clearly identifies the tool's function. It distinguishes from siblings by explicitly stating 'Unlike the forecast tools, this shows observed precipitation happening right now, not a prediction.'

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 provides explicit usage context: it says to use forecast tools for future weather and this tool for current observations. It also notes coverage is Sweden only, which is key for relevance. This gives the agent clear criteria for deciding between this tool and alternatives.

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