Invoker MCP Server

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

Annotations indicate readOnlyHint=false (mutation) and idempotentHint=true (safe to retry). The description adds valuable context beyond this: it specifies that the variable is set 'in the active environment' (scope) and will be used 'to resolve {{name}} placeholders in subsequent requests' (behavioral impact). This clarifies persistence and usage without contradicting annotations, though it doesn't mention rate limits or auth needs.

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 two sentences that are front-loaded with the core action and efficiently explain the purpose and impact. Every sentence earns its place: the first defines the tool, and the second clarifies its utility, with zero wasted words or redundancy.

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?

Given the tool's moderate complexity (mutation with idempotency), annotations cover safety aspects, and schema fully documents inputs. The description adds necessary context about the active environment and placeholder resolution. However, without an output schema, it doesn't describe return values (e.g., success confirmation), leaving a minor gap. Overall, it's mostly complete for the given structured data.

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%, with clear descriptions for 'name' and 'value' parameters. The description does not add any additional meaning beyond the schema (e.g., no format constraints or examples for placeholders). Since the schema already fully documents the parameters, the baseline score of 3 is appropriate, as the description doesn't compensate but also doesn't detract.

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 clearly states the specific action ('Set an environment variable') and the target resource ('in the active environment'), distinguishing it from siblings like 'invoker_add_environment' (which likely adds a new environment) or 'invoker_switch_environment' (which changes the active environment). It also explains the purpose ('used to resolve {{name}} placeholders in subsequent requests'), making the verb+resource+scope explicit.

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 implies usage by mentioning 'active environment' and 'subsequent requests', suggesting it should be used when configuring variables for future operations. However, it does not explicitly state when to use this tool versus alternatives (e.g., vs. 'invoker_add_environment' for environment-level changes) or any exclusions (e.g., not for temporary variables). The guidance is contextual but lacks explicit alternatives or when-not-to-use details.

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