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

Annotations already declare readOnlyHint, idempotentHint, non-destructive, and closed-world, so the safety profile is fully covered and the description needn't restate it. The description does add genuine behavioral value by disclosing the weekend/holiday adjustment rule and the three-way outcome classification. However, with no output schema, it should say more about the shape of the returned result (e.g., whether a date, a date plus a status string, or explanatory reasoning is returned).

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 front-loaded sentence that leads with the action and the resource, then enumerates the tax rules and the possible verdicts. It is long but every clause carries information; a bulleted or semi-colon split of the three outcome states would improve scanability slightly.

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 single-parameter, read-only calculator with no output schema, the definition covers what is computed, the governing rule nuance, and the interpretation of the result. It could be tighter about whether the 'filing today' verdict assumes a specific current date or the caller's date, which matters for reproducibility.

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 parameter already carries a detailed description of effective_date. The description adds only the light framing that this is 'the first day of the tax year, or the day a new business began,' which essentially mirrors the schema. With one fully documented parameter, the baseline of 4 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?

Names a specific verb and resource (calculates the Form 2553 deadline) and pins the exact scope: an S corp election effective on a given date. The close coupling to the single input parameter makes it trivially distinguishable from siblings like get_s_corp_election_rules or where_to_file_form_2553.

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 trigger condition is clear — you supply the intended effective date and get the deadline plus a timeliness verdict, which implicitly tells an agent this is a post-selection timing check rather than a rules lookup. It stops short of explicitly naming which sibling to use instead when the question is about eligibility or filing address.

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