getAvatar

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

The description discloses a critical behavioral trait: the file body is returned as UTF-8 text, which garbles binary files like images. Since avatars are images, it warns the tool is rarely useful. This goes beyond the readOnlyHint and openWorldHint annotations, which only cover safety and open-world assumptions.

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 with zero fluff. The core purpose is front-loaded, followed by a caveat and alternative routing. Every sentence earns its place.

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 one-parameter read tool with no output schema and readOnly annotation, the description covers all necessary context: what it does, the caveat about binary files, and which alternatives to use. Nothing an agent needs to call it correctly is missing.

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 input schema fully documents the single userId parameter (coverage 100%), so the baseline is 3. The description adds no extra meaning about the parameter itself—it's already obvious that userId identifies the user. The description focuses on the output behavior rather than the parameter semantics.

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 downloads a user's avatar image, which is a specific verb and resource. It distinguishes itself from siblings by naming getUser (for profile data) and updateAvatar (for replacement), so an agent can tell it apart immediately.

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?

Explicitly states when not to use the tool ('rarely useful') and names the exact alternatives (getUser for profile data, updateAvatar for replacement). This leaves no ambiguity about which sibling to choose.

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