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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety and side-effect profile is fully covered. The description adds only the output unit ('grout kg needed'), which is useful but minimal beyond the structured data.

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?

Five short sentences, front-loaded with the purpose and the return value. The trailing list_bundles pointer is mildly tangential but does not bloat the definition.

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 simple, single-output calculator the description is adequate: annotations carry the behavioral profile, an output schema covers the return value, and all four parameters are documented in the schema. Only a bit more routing guidance against sibling calculators would make it complete.

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%, so baseline is 3. The description names three of the four inputs (surface m², tile size, joint width) but omits joint depth (depth_mm) and adds no format, unit, or default semantics beyond what the schema already documents.

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 states a specific verb+resource ('Compute grout quantity for a tiling job'), which is distinct from the closest sibling calculate_tile_quantity. It does not, however, explicitly differentiate itself from that sibling, leaving the agent to infer the distinction between grout and tile counts.

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 renovation budget' is a vague context with no when-to-use condition, no exclusions, and no routing away from the many other construction calculators (tile_quantity, brick_count, plaster, etc.). The pointer to list_bundles is a navigation aid, not usage guidance for this tool.

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