download_icon

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

With no annotations, the description carries the full burden. It does disclose the key side effect (writes a file to the local filesystem) and the return value (saved file path), which is the most important behavior for a write tool. However, it says nothing about overwrite behavior, permissions, network/rate-limit constraints, or failure modes.

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?

Two sentences, zero waste, with the action and the source front-loaded and the return value last. Nothing is repeated from the schema.

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?

There is no output schema, but the description covers the return value explicitly, and all parameters are fully documented in the schema. For a simple single-file download tool the only real gap is the absence of overwrite/permission behavior.

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 100%, including defaults and the 'created if it does not exist' note on save_dir, so the schema already documents all six parameters. The description adds no parameter-level meaning beyond that, which is the baseline-3 case.

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?

States a specific verb and resource ('Download an icon's SVG file'), names the source (bioicons.com), and states the effect (save to local filesystem) plus the return value. This is clear enough to distinguish it from the read-only siblings (get_icon, get_icon_info), though it never names an alternative explicitly.

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 only implied: you use this when you need the SVG persisted to disk rather than fetched into context. No when-to-use/when-not guidance and no mention of when get_icon would be the better choice, so the agent must infer the distinction.

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