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

Annotations already declare openWorldHint=true, readOnlyHint=false, and non-idempotent behavior. The description adds genuinely valuable traits annotations cannot express: EU-only processing, an 'irreversible/flattened' output PDF, zero data retention, and an outbound-network prerequisite for /mcp/api/upload. However, it omits failure modes, size limits beyond the 45 KB base64 note, and what the caller receives back, which matters for a non-idempotent mutation.

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?

The core purpose is front-loaded in one dense sentence, then the operational rules are numbered and scannable. It is on the long side and the final URLs plus explicit UI click-path instructions ('clicking Redact then Open redacted PDF') are borderline excess, but every rule maps to a real fork in behavior.

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 six-parameter, zero-required, non-idempotent operation with no output schema, the description covers ingestion paths, upload prerequisites, policy defaults, and the human-review branch. An agent has everything needed to pick an input mode and invoke the tool correctly without further discovery.

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 every parameter is already documented at the field level, establishing a baseline of 3. The description adds procedural meaning the schema cannot — the ordering constraint that upload_id comes from POST /mcp/api/upload, and that file_url/document_base64 are substitute ingestion paths — but it does not clarify policy semantics or mutual exclusivity of the input sources beyond what the schema states.

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?

The opening sentence names a specific verb (identify and mask), two concrete domains (GDPR direct/indirect/Art. 9 and OSL/trade secrets), and the supported file types. It is immediately distinguishable from create_upload_link and fetch_reviewed_document, which are upload and retrieval helpers rather than the masking operation itself.

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?

Three explicit scenarios are enumerated (autonomous agents, chat attachments, interactive human chat), each with a prescribed action and, where relevant, the fallback. The sibling create_upload_link is named with the exact condition that triggers it, so routing decisions are fully determined.

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