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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, yet the description still adds real behavioral context: no API key or account required, the endpointUrl is never contacted, only AgentTrust's own observation history is read, and an unregistered URL degrades to { matched: false } rather than an error. That no-auth, no-network, no-error contract is exactly what an agent needs to decide whether calling this is safe and cheap.

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?

Front-loaded with the core purpose, then the cost/safety guarantees, then the return shape, then the edge case — a sensible ordering. Slightly repetitive: 'requires no API key' and 'does NOT contact endpointUrl itself' both appear to pre-empt the same worry about side effects, costing a little tightness.

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?

An output schema exists so return values need not be spelled out, and the description still summarizes the payload (status, ownership verification, reliability score, trustDecision) plus the not-found behavior. With annotations covering safety and the only edge case ({ matched: false }) called out, nothing material is left for the caller to guess.

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% and the parameter is single and well documented, so the baseline is 3. The description adds the 'exact invocation URL' requirement — i.e. matching is exact rather than fuzzy — plus the reassurance that the URL is used only for lookup, both of which are semantic value beyond the schema text.

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 verb and resource ('Pre-invocation trust check for an unknown AI agent or MCP server endpoint') and scopes it to one-shot, credential-free lookups, which implicitly separates it from the authenticated get_agent/get_agent_health siblings. It never names a sibling directly, so an agent must infer the boundary from the 'unknown agent / pre-invocation' framing rather than being told outright.

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?

'Pre-invocation' gives a clear triggering context — call this before invoking an agent you don't already trust, without an API key. There is no explicit when-not guidance (e.g. 'use get_agent instead when you already have a registered agent ID') and no alternatives are named, which is the only gap.

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