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

The annotations already declare readOnlyHint and idempotentHint, and the description adds meaningful behavioral context: full fee schedules vs scaled approximations for certain jurisdictions, the fact that the result states when it is an approximation, and the mention of waivers with an example. This goes well beyond the structured annotations.

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?

The description is dense but every sentence earns its place: purpose, usage trigger, jurisdiction keys, accuracy caveat, construction types, and an example. It is front-loaded with the core behavior and then provides necessary lookup data without redundancy.

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 13-parameter tool with no output schema, the description covers required parameters, jurisdiction semantics, construction types, and the accuracy difference between jurisdictions. It falls slightly short by not explaining the optional parameters, but the example and enum lists give an agent enough to make a reasonable call.

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?

With schema_description_coverage at 0%, the description must compensate, and it does partially: it defines jurisdiction keys, explains construction_type values, and gives a complete example with the required parameters. However, several optional parameters (stories, foundation_type, plan_check_speed, parcel_in_hillside, and the needs_* booleans) are left unexplained, which is a notable gap given zero schema descriptions.

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 uses a specific verb ('Estimate') and a clear resource ('building permit, plan check, sub-permit, state surcharge, school and impact fees for an ADU'), and even describes the output format ('itemized schedule with code citations and any waivers'). It clearly distinguishes this fee-estimation tool from siblings like get_adu_rules or get_rent_estimate.

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 description explicitly says 'Use for "what will permit costs" questions,' giving a direct usage trigger. It does not name alternatives or exclusion criteria, but the purpose is specific enough that an agent can route to it confidently.

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