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

Annotations already declare the non-destructive, non-idempotent write profile, so the lower bar applies. The description adds real value beyond annotations by disclosing the required 'los_measures:write' scope and the dependency-ordering behavior, though it says nothing about failure modes or return shape.

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, zero filler, and the core action is front-loaded ahead of the scope requirement and the prerequisite. Nothing could be removed without losing information.

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 16-parameter creation tool with a nested config object and no output schema, the description covers the two things the schema cannot convey: auth scope and how to obtain the required service_area_id. It stops short of explaining how data_source choices map onto data_source_config, which is the one remaining complexity left implicit.

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 every parameter including the enums and the nested data_source_config is already documented; baseline is 3. The description adds only the provenance of service_area_id, not any semantic detail the schema lacks.

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 ('Create a new LoS measure') plus its scope ('within a service area'), which distinguishes it from generic creation tools. However, it does not clarify how it differs from near-name siblings like create_los_measurement or create_los_proposed_target, so the agent must infer the boundary from naming alone.

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?

Gives an explicit prerequisite workflow ('Resolve service_area_id first via list_service_areas'), naming the alternative tool and the ordering constraint. It lacks any when-not guidance, but for a straightforward create tool the sequencing instruction is the key piece an agent needs.

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