list_instances

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered by structured data. The description adds genuinely useful behavior beyond that: results include per-instance auth usability, and the returned names are the identifiers other tools accept. It does not mention pagination, ordering, or failure behavior, but with zero params and an output schema those are minor.

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?

Two short sentences with no waste. The core purpose is front-loaded and the downstream-consumption note follows, which is the right ordering for an agent scanning definitions.

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 discovery tool with an output schema present, the description covers purpose, the extra auth-validity signal, and the role of its output in subsequent calls. Nothing an agent needs in order to call it correctly is missing.

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 no parameters, so there is nothing for the description to disambiguate; baseline for a 0-param tool applies. The sentence about other tools consuming the returned instance name is useful context, though it describes output rather than input semantics.

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 and resource: "List the configured ServiceNow instances," plus a second dimension of what is returned (whether each has a usable MCP auth method). It also ties itself to the sibling set by stating that the other tools consume the instance name returned here, so an agent can place it immediately in the workflow.

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?

The description makes the use case clear: call this to discover instance names that the other tools require, which is effectively a prerequisite/bootstrapping instruction. It does not state any when-not-to-use condition or what to do if no instance reports a usable auth method, leaving a small gap.

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