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

The description adds valuable behavior beyond annotations: 1-credit cost, write mode returns the PDF, temporary download link valid 15 minutes, and an explicit instruction to always include the link. This meaningfully informs the agent's user-facing behavior and does not contradict annotations.

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?

Three compact sentences, each carrying distinct operational value: mode behavior, cost, and response/link handling. The read/write distinction is front-loaded, and there is no filler.

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 9-parameter tool with no output schema, the description covers input mode, affected fields, output delivery mechanism, link expiry, cost, and required agent action. An agent has all call-time information needed to invoke the tool correctly and relay the result to the user.

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 the baseline is 3. The description adds key mode semantics: presence or absence of metadata fields switches between read and write. It lists the primary fields but does not add much per-parameter detail beyond the schema.

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 clear verb+resource pair: 'Read or write PDF metadata.' It also specifies exactly which fields are affected and the mode-selection rule, distinguishing it from sibling PDF tools like extract_pdf_text or fill_pdf_form.

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?

Provides explicit context for when to read vs write: no metadata fields means read, any field means write. It does not name alternatives or exclusions, but the tool's unique purpose among siblings makes this sufficient operational guidance.

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