get_v3_user_by_username

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

Annotations already declare readOnly/openWorld/non-destructive, but the description adds materially new context: it is a live TikTok request, billed at 1 request per call and 2-3 for a restored profile, and the response shape matches the v1 tool. Cost/rate behavior is exactly the kind of trait annotations cannot express. It stops short of describing latency or partial-failure handling, so not a 5.

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 tight sentences, front-loaded with the capability and the sibling routing, then cost and endpoint path. Every sentence carries distinct information with no repetition of the tool name or filler.

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 single-param read tool with no output schema, the description covers purpose, fallback trigger, cost, and endpoint. The one gap is that 'the response has the same shape' defers the return structure to a sibling rather than stating it, which mildly burdens the agent.

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?

One parameter with 0% schema description coverage; the schema only supplies min/max length. The description implies a username via the tool name and the GET path, but adds no format, casing, or '@'-prefix guidance beyond what the schema already shows.

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 ('Get a TikTok profile by username') and explicitly scopes it against the sibling get_v1_user_by_username, naming the case the v1 tool cannot serve (404 ProfileUnavailable). An agent can distinguish this tool from its nearest sibling without opening either schema.

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 says 'Use it as the fallback when the v1 tool fails' and names the exact failure condition that selects it. The when-to-use rule and the alternative are both stated, leaving nothing to inference.

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