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

Annotations already declare readOnlyHint, idempotentHint and closed-world, so the safety profile is covered. The description adds the default waste margin (10%) and the fact that output splits into tile count vs surface ordered, but omits behavioral detail that matters for a quantity tool, such as whether the count rounds up to whole tiles or accounts for tile orientation.

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 short sentences, front-loaded with the computation and its default, then the use case, then the return values. The trailing list_bundles pointer is mildly tangential to calling this tool but is short and clearly secondary.

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 pure read-only calculator with full schema coverage and an output schema, the definition covers purpose, typical use, and outputs adequately. Only the rounding/whole-tile behavior is unaddressed, which is a minor gap rather than a blocker for correct invocation.

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 units and defaults already documented per property, so the baseline is 3. The description only re-lists the inputs ('surface m², tile size, waste %') without adding range, unit-conversion or interaction semantics beyond what the schema states.

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 ('Compute tiles needed') plus the distinguishing feature of a waste margin, and names what it returns (tile count and surface ordered). It does not explicitly differentiate itself from the similarly named sibling calculate_tile_grout, which is the one confusion an agent could plausibly hit.

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?

'Use for floor or wall tiling' gives a clear domain context for invocation, and the pointer to list_bundles offers a routing path for related construction calculators. It stops short of naming when NOT to use it or a competing sibling, so it is clear context without exclusions.

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