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

Beyond the readOnlyHint/openWorldHint/destructiveHint annotations, the description discloses rich behavior: simplified pathOnMap at ~50m, render_payload for full resolution, geometryDegraded meaning, patternsTotal semantics, matchedTotal indicating an excerpt, note for unknown areas, candidate list on ambiguity, and a strong anti-fabrication directive. This exceeds what annotations alone provide.

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 long but highly structured with bold labels (Pflicht, Optional, Die Antwort, Mehrdeutig, Grenzen, Nicht dafür, Anleitung, Anti-Fab) and front-loads the core purpose. Every section earns its place by covering a distinct operational aspect of a complex tool, and the density is justified by the absence of an output schema and the large sibling set.

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?

Given six parameters, no output schema, and numerous sibling tools, the description is exceptionally complete: it covers required inputs, response shape, candidate handling, degraded geometry, limits, what the tool is not for, and anti-hallucination guidance. An agent has all the information needed to invoke it correctly and interpret results.

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?

Although schema coverage is 100%, the description adds substantial meaning: human-written query matching ('Heide-Shuttle', 'HS 2'), id from a previous answer being exactly one line, area disambiguating lines numbered '100', limit default 8 and capping at 15, and render_payload behavior. These details are not fully evident from the schema alone.

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 clearly defines the tool as the line course of an ÖPNV line (stops sequence and drawn route) and distinguishes it from sibling tools by naming alternatives: A→B connections, departures, disruptions. It even gives example questions ('wo fährt die Y entlang', 'welche X-Linien gibt es'), so an agent can recognize when to select 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?

It explicitly states that for line questions this tool should be used rather than general knowledge, and it names excluded cases: connections, departures, disruptions. The mandatory query-or-id requirement, fallback instruction to ask when ambiguous, and pointer to get_usage_guide provide clear decision guidance.

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