list_service_layers

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

With no annotations, the description carries the full burden and discloses the return contents ('each layer's id, name and geometry'), the purpose of the output ('pick the right layer_id'), and a real operational quirk ('Yerevan services often skip layer 0'). It does not cover auth requirements or failure modes, but for a read-only listing tool this is meaningful behavioral context.

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?

Two sentences, roughly 37 words, with the verb and scope front-loaded. The layer-0 warning earns its place as actionable domain guidance, and there is no filler.

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 single-parameter tool with a fully documented schema and no output schema, the description covers the essentials: what it operates on, what it returns, and how to use the result. The 'skip layer 0' insight adds real value. It could mention error behavior for invalid paths, but nothing critical is missing for correct invocation.

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 the schema already providing an example path and noting Armenian is allowed and /FeatureServer is optional. The description adds no parameter-level detail beyond what the schema documents, so the baseline of 3 applies.

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-resource pair ('List the layers and tables inside a raw ArcGIS service') and immediately scopes the tool to 'services that aren't in the curated catalog', which distinguishes it from siblings like search_layers and describe_layer. An agent can tell exactly what this tool does and why it exists.

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 phrase 'for exploring services that aren't in the curated catalog' gives clear context for when to invoke this tool, implicitly contrasting with catalog-based siblings. However, it does not explicitly name an alternative tool or state when-not-to-use it, so it stops short of the top score.

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