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

Annotations already declare this a read-only, idempotent, non-destructive, closed-world lookup, so the safety profile is covered. The description adds genuine value beyond that by disclosing the shape of the answer: plain-English meaning, the underlying IRS rule text, and remediation guidance. It does not say what happens for an unrecognized or non-MEF code, which keeps it short of full transparency.

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?

One sentence, front-loaded with the deliverable and immediately followed by the scope and a code example. Nothing is wasted and nothing important is buried.

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, so the description must describe the return value, and it does so by enumerating the three components it produces. For a single-parameter lookup with full annotation coverage that is nearly sufficient; only the miss behavior (unknown or malformed code) is left unaddressed.

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% and the single 'code' parameter is documented with an example and length bounds, so the schema carries the parameter burden. The description repeats the same example format and adds the form-family scope, but contributes no new syntax or validation detail beyond the schema.

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 names a specific resource (an IRS Modernized e-File business rule reject code), scopes it to four named forms, and gives a concrete example ('R0000-922-01'). No sibling tool touches reject codes, so an agent can distinguish this tool from check_exempt_status, which_990_form, and the rest 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?

The context of use is implied rather than stated: an agent must infer that this is for decoding a rejection after a failed e-file submission. There are no explicit exclusions or pointers to alternatives (none exist among the siblings, but the description doesn't say so). Adequate but leaves the when-to-call trigger to inference.

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