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

Annotations already flag destructive=true, idempotent=false, openWorld=false-write behavior, and the description adds genuinely non-obvious traits: the public link survives the replacement, expectedRevision guards against stale overwrites, and static HTML has a precise support/unsupported boundary (no scripts, handlers, images, SVG, external deps, forms, meta). This is real behavioral detail beyond the structured fields.

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?

Four sentences, front-loaded with the irreversible core operation and the preservation guarantee; the restrictions list is long but each element is actionable. Slight density in the final enumeration, but no filler 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?

For a destructive mutation with no output schema, the description covers what is replaced, what is preserved, concurrency safety, and content-format limits, so an agent can call it correctly. It omits what the response contains (e.g., the new revision needed for the next update) and whether fields outside content (sharing, publication state) are touched.

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 coverage is 0%, but property names and const values are largely self-documenting; the description still contributes meaning by explaining the html+mode=static combination, the producer of viewport/security metadata, and the semantic purpose of expectedRevision (stale-overwrite prevention). It does not clarify the id parameter or the block-variant constraints (maxItems, maxLength), so it is not fully compensating.

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 ('Replace a brief's content') plus the distinguishing non-obvious effect ('while preserving its existing public link'), which separates it from create_document/delete_document and from publish/unpublish siblings. An agent can identify the operation without opening the schema.

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?

Usage context is implied rather than stated: the description explains that revision matching prevents stale overwrites and that two content modes are supported, which tells the agent what it must supply, but it never names when to prefer this tool over siblings such as save_document_from_app or publish_document, and gives no exclusions or prerequisites (e.g., needing the current revision from get_document).

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