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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the description adds useful context instead: data source (TfL Journey Planner), the 09:00 weekday departure assumption, quickest-first ordering, and that the district's quickest sector is included. It stops short of describing failure behavior for unrecognised districts.

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 core purpose, source, timing assumption and ordering are front-loaded in the first clause. The trailing 12-hub enumeration is long, but it is the only place the readable hub names appear, so it largely earns its space.

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 does carry the return-format burden and handles it well (minutes, quickest first, quickest sector). Missing only edge-case detail such as what happens for an invalid or unrecognised district, which the check_london_postcode sibling could have been referenced for.

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 coverage is 100%, so baseline is 3, but the description adds genuine value by mapping each enum slug to its human-readable hub name (e.g. canary-wharf to Canary Wharf, city-of-london to Bank / Liverpool Street / Moorgate), clarifying ambiguous codes the raw enum does not explain.

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 with full scope: door-to-door public transport minutes from a London postcode district to named work hubs. It clearly distinguishes the tool from siblings like compare_london_districts and get_district_profile by naming the origin/destination framing and the quickest-first output.

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?

Usage is implied by the scope (one district against one or all hubs), and the hub omission default ('leave out for all 12' via schema) is helpful. However, there is no explicit guidance on when to use this versus compare_london_districts or get_district_profile, nor any stated precondition that the district must be valid.

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