invariance_operator_me

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds useful context about credential-backed operator identity, but it does not disclose details like the return shape, whether identity can change, or how credentials are resolved. This is acceptable given the strong annotations, but the description could add a bit more behavioral insight.

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 three sentences with no filler. The first sentence states the action, the second defines the key concept, and the third gives concrete usage contexts. Every sentence earns its place and the most important information is front-loaded.

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 no-parameter, read-only identity lookup, the description is nearly complete: it defines the domain concept, states what the tool shows, and gives practical scenarios for use. The only minor gap is that it does not explicitly describe the return format, but 'Show the operator identity' sufficiently implies the output for an agent.

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 has zero parameters, so the baseline is 4. The description adds semantic context by explaining what an 'operator' is and what the returned identity represents, which is valuable even though there are no parameters to document.

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: 'Show the operator identity associated with the current credentials.' It also defines 'operator' as the unified actor model, which clearly scopes the tool's meaning and separates it from generic identity tools. This is more than a restatement of the name and gives an agent a concrete understanding of what it does.

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 explicitly tells the agent when to use the tool: 'Use this to confirm which operator context the MCP server is acting as,' with concrete examples like before recording session events or attaching runs. It does not explicitly identify alternatives or when not to use it, so it stops just short of full routing guidance.

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