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

The annotations already declare read-only and idempotent behavior, but the description adds valuable context beyond that: it discloses best-effort behavior, returns nothing for scans (no OCR), returns glyph indices for custom-encoded fonts, and states that the tool will indicate which case applies. It also mentions the unlimited free tier, which is helpful operational context.

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 concise, front-loaded with the primary purpose, and uses four short sentences with no wasted explanation. The 'Read-only' sentence is slightly redundant with the annotations, but the overall structure is tight and effective.

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 tool with no output schema, the description adequately explains what to expect from the return value: normal extracted text, nothing for scans, or glyph indices for custom fonts, plus an indicator of which case applies. Combined with schema-documented parameters and annotations, the agent has enough information to use the tool correctly.

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 path and pages parameters are already documented in the input schema. The tool description does not add parameter-level detail beyond what the schema provides, so the baseline 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 clearly states the verb and resource: 'best-effort text extraction' from PDFs. It distinguishes the tool from siblings like pdf_info and pdf_pages by focusing specifically on text content rather than metadata or page operations, and it explicitly describes the scope and limitations.

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 explicitly tells the agent when to call it: 'Call this tool for best-effort text extraction from standard-font PDFs.' It provides clear context for use, though it does not name alternative sibling tools or explicitly state when not to use it beyond the scan/custom-font edge cases.

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