Clone a function and retain a reusable closure reference

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower, and the description earns credit by disclosing the non-obvious retention mechanism: results land in getgenv().__mcp_closure_refs because functions can't cross JSON. It also names a produced handle type, though it doesn't explain lifecycle/release of the handle.

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?

Front-loads the purpose in the first sentence, then packages operational metadata into compact semicolon-delimited clauses. Information-dense with little waste, though the trailing 'On failure: inspect tool-schema...' clause is generic boilerplate.

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?

Despite no output schema, the description explains the return value (a reusable Reference expression stored in a named global), covers prerequisites, and flags a failure fallback. Complete enough for a 3-param tool, with only minor gaps around handle lifecycle.

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% and each parameter is well documented in the schema, so baseline 3 applies. The description's signature line (functionPath, threadContext, key) merely restates what the schema already provides and adds no new semantic detail.

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?

States a specific verb (clone) and resource (function) and explains the mechanism and outcome: the result is retained in getgenv().__mcp_closure_refs and returned as a reusable Reference. This is clearly distinct from sibling closure tools (inspect-closure, get-closure-protos, invoke-closure), which don't produce reusable handles.

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?

Provides operating context via 'Phase: observe', 'Requires: active-client, resolved-target', and 'Produce: created-handle', which imply when the tool is usable. However, it never states when to prefer ou clone-function over alternatives like inspect-closure or get-closure-protos, nor any exclusions, so it only implies usage rather than routing.

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