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

Annotations are sparse (only readOnlyHint/idempotentHint/destructiveHint), so the description carries real load: it discloses the 3-calls-per-day rate limit, the 4000-character cap, the no-API-key/no-email/no-signup auth requirement, and the exact return payload (structured data, confidence, review_needed flag). These are concrete operational facts an agent cannot get from structured fields.

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 sentences, front-loaded with the value proposition, then the input contract, then the return shape and escalation path. No filler, no restatement of the title.

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?

With no output schema, the description compensates by naming the returned fields and their parity with the paid tools, and it covers limits, auth, and alternatives. For a 4-parameter extraction tool this is sufficient to call 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 coverage is 100%, so baseline is 3. The description adds example text types (invoice, receipt, resume, scraped HTML, email body) and frames schema/schema_id as constraining the result, but it never mentions the `instructions` parameter at all, so it does not meaningfully exceed what the schema already documents.

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 ('Run a REAL extraction', parse messy text into JSON) and immediately frames it against the paid siblings parse_text/parse_document. An agent can tell this is the zero-auth trial path without opening any schema.

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?

Explicit when-to-use (see output shape before committing), when-not (real volume), and the exact alternative route ('call create_api_key for 50 free credits, then use parse_text or parse_document'). It also points to list_schemas for the schema_id set. Nothing is left to inference.

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