BCD — Bridge Control Delegate

write_file

Destructive

Create or replace a file; mode append adds to the end. .docx paths take Markdown; .xlsx/.xls/.xlsm take a JSON 2D array or an object of named sheets. The parent folder must exist (mode overwrite creates it). Rewrites are atomic. To change part of an existing file use edit_block; for PDFs use write_pdf.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`mode`	No		rewrite
`path`	Yes
`content`	Yes
`deviceId`	No	Computer name or id from list_devices. Optional with one computer online or a default set.
`workSessionId`	No	Work session from create_work_session. Pass the same ID on every call in this conversation; omit for legacy unscoped work.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 30, 2026

addedInput schema / properties / workSessionId

Added value: +{
+  "description": "Work session from create_work_session. Pass the same ID on every call in this conversation; omit for legacy unscoped work.",
+  "format": "uuid",
+  "type": "string"
+}

First observedSep 30, 2026

TDQS

A4.9/5.0

Behavior5/5

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

Annotations declare destructiveHint=true/readOnlyHint=false, and the description adds non-obvious behavior beyond them: 'The parent folder must exist (mode overwrite creates it)' and 'Rewrites are atomic.' These are real operational facts an agent could not infer from the schema.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Four dense sentences, purpose front-loaded, each carrying distinct information (mode, formats, prerequisites, alternatives) with no filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given no output schema and a mutation tool, the description covers purpose, format handling, prerequisites, atomicity, and sibling routing. Nothing essential for correct invocation is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With only 40% schema coverage, the description compensates by explaining mode=append and the overwrite-creates-parent behavior, plus format-specific content handling (.docx takes Markdown, .xlsx takes a JSON 2D array or named-sheet object). It adds genuine meaning for the undocumented parameters, though path and deviceId/workSessionId remain schema-only.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

Starts with a specific verb+resource ('Create or replace a file') and immediately names the sibling tools it is not (edit_block for partial edits, write_pdf for PDFs). An agent can distinguish this from edit_block/write_pdf without opening any schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicit routing: 'To change part of an existing file use edit_block; for PDFs use write_pdf.' It also states the mode semantics (append adds to the end) so the agent knows which mode to select for which intent.

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

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