ws:Send — send a frame over an open WebSocket

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

Annotations already declare destructive=true, idempotent=false and openWorld=true, but the description adds real behavioral detail beyond them: the registry lookup, an open-socket check, pcall wrapping, and the exact failure surface ({ error } on unknown id, closed socket, or Send failure). The 'MUTATING / external network I/O' line merely restates the annotations, which keeps it short of a 5.

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-loaded and information-dense, but the trailing metadata block (Phase, cost, idempotency, capabilities, Produces, Verify with, Safety, On failure) repeats concepts already stated in prose or annotations, and the closing 'inspect tool-schema' pointer is boilerplate rather than tool-specific value.

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?

With no output schema, the description supplies the return contract ({ id, sent = true } or { error }) and the failure conditions, plus prerequisites and safety framing. For a 3-param mutating socket-write tool, nothing an agent needs 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?

Schema description coverage is 100%, so id (registry id from ws-connect), message (text frame) and optional threadContext are fully documented in the schema. The description's Signature line and registry-lookup narrative confirm but do not materially extend that per-parameter meaning; baseline 3 applies.

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 precise verb+resource+scope: sends a text frame over a WebSocket opened by ws-connect, addressed by registry id. It also names the exact internal mechanism (getgenv().__mcp_ws[id], socket:Send), so an agent can distinguish it cleanly from ws-connect, ws-receive and ws-close.

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?

Names the prerequisite tool explicitly ('previously opened with ws-connect') and lists gating requirements (active-client, explicit-mutation-approval), giving clear context for when the tool is callable. It does not, however, spell out when an agent should prefer this over alternatives or what to do if no socket exists.

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