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

Annotations already cover the safety profile (readOnlyHint=true, openWorldHint=false), so the bar is lower, and the description adds real value by publishing the exact formulas for sections, posts and pickets, including the ceil rounding. It omits the rails formula itself and any note about waste/overage, which keeps it from 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?

Two dense sentences with zero filler: the scope constraint leads and the computation follows immediately. Every clause carries information an agent can act on.

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 zero-required, fully documented calculator with no output schema, the description supplies the derivation logic an agent needs to predict results. It stops short of describing the return shape or units, and silence on whether waste allowance is included leaves a minor gap.

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%, with defaults documented for all six parameters, so the baseline is 3. The formula adds meaning to length, spacing, picket width and gap, but rails_per_section is never referenced, so the description does not fully compensate beyond what the schema already provides.

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 computed resource set (posts, rails, pickets) and scopes it to 'a straight run of wood privacy or picket fence', which implicitly separates it from siblings like calc_deck_board or calc_concrete_slab. It does not name any sibling explicitly, so it stops short of a 5.

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 'straight run' qualifier implies the tool is not for corners, angled runs, or other fence geometries, which is useful scoping. However there is no explicit when-to-use statement, no alternatives named, and no mention of when this calculator should not be reached for.

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