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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety bar is pre-met; the description adds the auth detail that it "works with mcp:read tokens," which is real operational context not in the annotations. It also discloses the result envelope (data plus defaultRegions), though that partly duplicates the output schema.

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, front-loaded with what the tool is, then return shape, then how to use the output, then auth scope. No filler, and the downstream-use instruction comes before the least-important token note.

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?

Since an output schema exists, the return-value sentence is technically redundant, but everything an agent needs — purpose, token requirement, and how to apply the slugs — is present. Nothing material is missing for a zero-parameter read tool.

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 tool takes zero parameters, so there is nothing to disambiguate and the baseline is 4. However, the description spends a sentence describing the return payload rather than parameter behavior, so it adds no semantic value on this axis.

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?

Specific verb+resource ("List monitoring regions available to the organization") with concrete slug examples (eu-west-1, us-east-1). It also distinguishes scope: org-visible regions plus the org's defaultRegions set, which no sibling tool returns.

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 routes downstream use: "Use these slugs in the regions array of create_check or update_check," which tells the agent exactly why it would call this before those mutation tools. It doesn't name an alternative listing tool, but none exists among the siblings, so the guidance is effectively complete.

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