Update document metadata

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

It discloses several behavioral traits: the update is incremental, XMP stays in sync on PDF/A documents, /ModDate is refreshed, earlier revisions and signatures remain byte-identical, and the new revision is unsigned. These details go well beyond the annotations and explain consequences that materially affect an agent's subsequent decisions.

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 purposeful sentences stretch the agent exactly what it needs: what the tool does, what else is affected, what is preserved, and when not to use it. There is almost no redundant phrasing, and the most important facts are front-loaded.

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?

Given the tool's complexity, the 100% parameter coverage, and the presence of an output schema, the description covers the remaining operational concerns: encrypted-source failure, signature preservation, XMP behavior, and reproducibility. An agent has enough context to select and invoke this tool correctly and to plan follow-up actions such as re-signing.

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?

The input schema already describes all 8 parameters with 100% coverage, so the description does not need to restate them. The only added parameter-level guidance is the modDate pinning tip ('same host TZ'), which the schema also partially captures. This adds marginal value, so the baseline score of 3 is appropriate.

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 description opens with a specific verb and resource: 'Rewrite /Info (title, author, subject, keywords) of an EXISTING PDF as an incremental update.' It makes the scope precise and distinguishes itself from metadata files placed at document generation time by pointing to the `metadata` option of document tools, so an agent can separate this from `generate_basic_pdf` and similar.

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?

The last sentence is an explicit routing rule: 'For metadata at generation time use the `metadata` option of the document tools.' The description also gives conditional guidance for encrypted sources and for whether a signature needs to be reapplied (sign_pdf / timestamp_pdf again), which tells an agent what to do before and after this tool.

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