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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds the meaningful scoping detail that markets live in a per-agent namespace, which explains why a negative result is not global; however, that nuance largely restates the title's 'this agent' phrasing and adds nothing about freshness, caching, or query cost.

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 short sentences, front-loaded with the operation and followed by the namespace qualifier. No filler, no restated boilerplate, and the most important constraint arrives before any caveat.

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?

With one parameter, an exhaustive annotation set, and an output schema covering the return value, the description only needs to establish intent and scope — both of which it does. The remaining gap is workflow guidance (what to do on true vs false), which is arguably adjacent to this tool's scope.

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 0% — the input parameter is an untyped string with only length bounds — so the description carries the semantic load. It explains that externalId is the identifier the agent itself supplied when deploying, which is real meaning beyond the schema, though it does not state the format, whether case sensitivity applies, or how a missing/mismatched id is treated.

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 check (does a market already exist) keyed on a named identifier (externalId), which is a distinct verb+resource combination an agent can recognize. It does not name a sibling tool to contrast with, but none of the siblings overlap this exact idempotency check, so differentiation is implicit rather than spelled out.

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 description implies the use case — verifying prior deployment before re-deploying with a given externalId — but never states it explicitly, nor does it say when not to use it or what to do with the result (deploy vs skip). The agent must infer the workflow from the title's 'Idempotency check' framing.

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