Run an MCP tool call in the VM

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

Adds rich behavior beyond annotations: snapshots are taken automatically before and after, a step record is produced, reason/expected/afterIntervalMs are optional overrides, and the result returns the after-snapshot as 'pending' without waiting. It also explains the background download and that relay_image/relay_finish/relay_release handle it, plus the replay caution.

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 core action and keeps each sentence purposeful, though it is dense and some sentences duplicate schema content that could be trimmed. Size is defensible for a multi-target relay tool.

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 complex 7-parameter tool with no output schema, the description covers the essential runtime contract: forwarding semantics, automatic evidence, the async image flow and which siblings wait for downloads. It omits mention of timeoutMs behavior, but the schema covers that adequately.

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%, so the baseline is 3. The description largely restates schema content ('target is cua..., tool and args forwarded unchanged', optional overrides), adding little meaning beyond what the schema already documents, so no credit above baseline is warranted.

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 and resource: 'Send one tool call to an MCP server inside the VM', and enumerates the three valid targets. It differentiates from relay_tools (discovery) but never distinguishes itself from closer siblings like relay_exec or relay_script, leaving an agent to infer the boundary.

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?

Gives actionable context: 'Use relay_tools to see a target's exact tools' and the caution 'Never replay an uncertain call.' However it offers no explicit when-not guidance or comparison against relay_exec/relay_script, so alternative selection is only partially covered.

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