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

Annotations already declare readOnlyHint, openWorldHint and idempotentHint, but the description adds real behavioral substance: the widget renders three panels and the WebSocket panel is deliberately not offered because the feed needs a credential that is not passed to a widget. That sandbox/credential limitation is not in any structured field.

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?

Front-loads the one-line purpose, then mechanism, then the when-to-use line, then args. The parenthetical about the WebSocket credential is a little winding, but every sentence carries information and nothing is padding.

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-parameter diagnostic with an output schema present, the description covers purpose, mechanism, trigger condition and the argument. Return-value details are legitimately left to the output schema, so no critical gap remains.

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 0%, so the description must carry the parameter burden, and it does partially: 'symbol: G7 pair to stream (default EURUSD)' adds domain meaning ('G7 pair') and restates the default. It does not specify accepted symbol format or casing, but it adds value beyond the bare schema property.

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: 'test whether LIVE data streaming works in this client.' It also explains the mechanism (renders a widget with JS timer, WebSocket, HTTP poll panels), which clearly differentiates it from read siblings like get_quote or get_model_chart.

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?

Gives an explicit trigger condition: 'Use when a live/ticking chart isn't moving.' That is clear context, though it does not name which sibling to prefer instead (e.g. get_quote, get_model_chart) or describe when not to use it.

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