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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds value beyond that: the upstream source (FederalRegister.gov API), the 1-credit cost, the shape of the returned record, and the important limitation that full text is excluded and must be fetched via html_url or pdf_url. It does not discuss failure modes for an unknown document number, which keeps it short of a 5.

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?

Front-loaded with the verb and key, then audience, source, constraints and cost in a logical order; no filler sentences. Minor waste from restating the '90 FR 8443' exclusion that the schema already carries, but overall tight for the amount of information conveyed.

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?

There is no output schema, and the description compensates by listing the fields returned (type, agencies, publication/signing dates, FR citation, effective date, comment deadline, docket, official PDF). Combined with the cost note and the full-text redirect, an agent has everything needed to call this correctly and to know what to do with the result.

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?

With a single parameter at 100% schema coverage, the schema already defines document_number and even includes the 'not an FR page citation such as 90 FR 8443' caveat. The description repeats that same distinction rather than adding new meaning such as format normalization or behavior on ambiguous numbers, so the baseline of 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 ('Fetches one Federal Register document by its document number') and immediately enumerates what the record contains (type, agencies, dates, FR citation, docket, govinfo PDF). It also distinguishes itself from adjacent concepts by naming what it is not: not a citation resolver and not a full-text source. No sibling tool covers this exact primary-record lookup, so the scope is 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?

Gives an explicit audience and precondition ('who have the document number from a notice, docket or URL and want the primary record rather than a secondary summary'), which tells the agent both when to pick this and when a summary tool is preferable. It also states two negative conditions — it will not resolve '90 FR 8443' and will not return full text — and redirects to html_url/pdf_url for the latter.

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