Routes of a line

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

Annotations already establish readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds genuine domain context beyond that: the geographic coverage limit (Attica only, OASA buses/trolleys/metro/tram) and the typical outbound/return/night/weekend route structure. It does not describe return format or ordering, but with annotations present the bar is lower.

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 sentences, front-loaded with what is returned, followed by the domain context and the scope limit. Every sentence earns its place with no repetition of the title or schema.

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 two-parameter lookup with no output schema, the description covers purpose, scope, and one key return field (route_code) that downstream tools consume. It could say a bit more about the returned shape (e.g., how routes are identified), but nothing essential to calling it correctly is missing.

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%, with both parameters documented in-schema, including the accepted identifier forms and the language enum. The description adds no additional parameter detail (it never mentions the language option), so baseline 3 is correct when the schema does the heavy lifting.

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 resource ('the direction variants (routes) of one OASA line') and even previews the payload ('with destination and length'). This distinguishes it from siblings like route_stops, route_shape, and list_lines, which an agent can rule out without opening a schema.

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 concrete routing cue: 'Other tools need the route_code from here,' which tells the agent this is a prerequisite step in a chain. It also scopes applicability ('Covers Attica (greater Athens) only'). It stops short of naming an explicit alternative or when-not-to-use condition.

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