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

Although annotations already declare read-only, idempotent, non-destructive behavior, the description adds substantial operational guidance: lead with each site's `disclosure`, relay `measurementNote` when `measurementHealthy` is false, and never invent figures when `coverage` is 'none'. These are behavioral constraints beyond the structured fields and are essential for correct use.

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?

The description is front-loaded with the core purpose, then immediately routes to the alternative tool, then states critical response-handling rules. Despite its length, each sentence serves a distinct selection or usage purpose, with only minor redundancy in the trailing 'Read-only.'

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 read-only monitoring tool with no output schema, the description supplies the missing behavioral context: historical vs live scope, optional domain behavior, and how to handle `disclosure`, `measurementHealthy`, `measurementNote`, and `coverage`. That is enough for an agent to call and interpret the tool correctly.

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%, so both `days` and `domain` are already documented in the schema. The description mentions domain scoping and notes that scoping returns recent outages, but this largely duplicates schema wording and does not add new syntax or interpretation beyond it.

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 uses a specific verb and resource: 'Returns MEASURED uptime history for the customer's own hosted sites' over a trailing window from SLA monitoring. It explicitly distinguishes itself from the sibling check_uptime, so an agent can tell which tool to pick 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?

It gives explicit when-to-use examples ('how has my site been?', 'has my site gone down?', 'did you have an outage last week?') and a direct when-not rule contrasting with check_uptime for live 'is my site up?' checks. The optional domain scoping behavior is also described.

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