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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered structurally. The description still adds real context: single-file scope, 'permitted local PDF' on a 'paired computer', and that only annotation metadata is returned. It re-states the non-mutating claim, which is partly redundant with the hints.

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?

Two sentences, front-loaded with the usage trigger, followed by prerequisites and non-mutation scope. No filler or repeated clauses; every sentence carries information.

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?

Covers the trigger, single-file scope, required input, and the fact that it performs no writes. An output schema exists, so return values need not be described. The only mild gap is that it doesn't mention the device/pairing requirement explicitly, though the schema makes it mandatory.

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 both parameters (path, device) are already documented in the schema. The description only restates that the PDF path is required and adds no format, constraint, or example beyond that, so the baseline 3 applies.

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 ('list or inspect annotations, comments, highlights or markup') and scopes it to a single local PDF, which cleanly separates it from siblings like pdf_extract_pages, pdf_merge, or pdf_info. The negation ('does not edit, save, delete or annotate') further pins down the boundary.

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?

Gives an explicit trigger ('Use this when the user asks to list or inspect annotations...'), which is exactly the invocation condition an agent needs. It does not name alternative siblings (e.g. pdf_info) for the case where a user wants general PDF metadata, so it stops short of full routing guidance.

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