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

With no annotations, the description carries the burden of behavioral disclosure. It provides meaningful context: the comparison is byte-based, it reports relationships rather than judgments, and it examines specific aspects (pages, metadata, signature events). This goes beyond the schema, though it doesn't explicitly mention read-only behavior or failure modes.

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 description is two sentences with no filler. The first sentence immediately states the action and resource, and the second sentence clarifies the output scope. Every word earns its place.

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 no output schema, the description should clarify what the tool returns. It states it reports the relationship and lists the comparison dimensions, which gives a fair understanding. It lacks a detailed output format, but for a moderately complex tool, this is reasonably complete.

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 each parameter (file_a_base64, file_b_base64, filename_a, filename_b) is adequately documented. The tool description adds no parameter-specific meaning, but none is needed; 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?

The description clearly states the verb 'Compare' with the resource 'two PDFs' and specifies the comparison dimensions: byte identity, derivation, and changes in pages, metadata, and signature events. It also explicitly distinguishes from sibling verify tools by noting it does not decide which file is correct, making the purpose unambiguous.

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 description implies the tool is used for comparing two PDFs, and the note about not deciding the right file sets expectations. However, it does not explicitly state when to use this tool over alternatives like verify_pdf, nor does it provide 'when not to use' guidance. No alternatives are named.

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