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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds genuine behavioral context those annotations cannot: the tool never fabricates figures and returns null when a value is not stored, which tells the agent how to interpret missing data. It stops short of saying whether one row or many are returned per trail.

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, each carrying distinct payload: return shape first, then routing, then data-fidelity caveat. Nothing is redundant and the most decision-relevant information is front-loaded.

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?

With no output schema, the description correctly compensates by naming the returned columns and the null convention. For a single-parameter read tool with full annotation coverage this is close to sufficient; only the row cardinality and the meaning of 'costLocal' (presumably local currency) are 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?

The schema has 100% description coverage, documenting the single 'trail' parameter as 'Slug or trail name', so the description starts at the baseline. It adds no syntax, format, or resolution guidance (e.g. how slug vs display name is matched) beyond what the schema already supplies.

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 ('Returns permit fee rows') and immediately enumerates the returned fields (costLocal, issuer, readDate, tier), which pins down what an agent actually gets back. It explicitly distinguishes itself from get_trail, though it does not clarify its boundary against plan_permits, which also concerns permits/booking and could be confused with it.

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 a clear when-to-use clause ('Use for fee and booking questions') plus a named alternative for a different concern ('use get_trail for distance and grade'). The routing guidance is concrete but incomplete — the sibling set includes plan_permits and get_provenance, and neither is addressed.

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