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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is settled. The description adds scope detail beyond that — that it covers per-feed outage state and lookback windows of 1/7/30/90 days — but says nothing about freshness of the status itself, caching, or granularity of the 'down' determination.

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?

One compact sentence that front-loads the most actionable information (is data live right now). It is a sentence fragment rather than a full clause, which is a small stylistic cost, but nothing is padded or repeated.

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 zero-parameter, no-output-schema tool, the description covers the essentials: what questions it answers and the time ranges involved. An agent could call it correctly. It stops short of describing the response shape, which matters here because there is no output schema to fall back on.

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?

With zero parameters and 100% schema coverage the baseline is 4, but the description explains none of the fixed dimensions it returns (liveness vs. feed outages vs. historical windows) as parameters or selectors — notably whether the 1/7/30/90-day windows are all returned at once. Minor deduction for an all-defaults tool whose output shape is only vaguely sketched.

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 names the concrete resource and what aspect of it is reported: current liveness, which exchange feeds are down, and availability over four time windows. It is a noun phrase rather than a verb+resource ('check service status'), but it is specific enough that an agent can tell this apart from the market-data siblings like exchanges or exchange_overview.

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?

There is no statement of when to call this versus alternatives — no mention of calling it before other tools, no preconditions, no exclusions. The only implied usage is 'if you need to know whether data is live,' which the agent must infer from the noun phrase.

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