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

With no annotations provided, the description carries the full behavioral burden. It explicitly states 'Read-only' and 'No authentication required', and goes further to disclose what the tool does not return, providing strong transparency about its behavior and boundaries.

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 three sentences, front-loaded with 'Read-only' and the primary action. Each sentence earns its place: the first defines scope and output, the second gives usage guidance, and the third clarifies exclusions. No redundancy or fluff.

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?

Despite having no output schema, the description lists the exact fields returned (slug, name, description, category, provider, endpoint count, lowest price). With only one optional parameter and clear exclusions, the tool is simple enough that this description fully covers its context and behavior.

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 description coverage is 100%, with the single 'limit' parameter fully documented in the schema (default, minimum, hard cap, clamping behavior). The tool description adds no additional parameter context beyond what the schema already provides, so the baseline of 3 is appropriate.

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 states the tool 'lists onboarded APIHub services alphabetically' and enumerates the specific fields returned. It explicitly distinguishes from siblings by noting exclusions ('does not include external x402 APIs', 'does not return endpoint-level details') and points to alternative tools, making its purpose unambiguous.

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?

Provides explicit when-to-use guidance: 'Use this to browse the full onboarded catalog when you don't have a specific capability in mind'. It also names alternatives for filtering (apihub_search), external APIs (apihub_search_external), and endpoint details (apihub_get_service), giving clear usage boundaries.

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