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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds a genuinely non-obvious behavioral detail — 'per-agent namespace' — which tells the agent that a negative result only means this agent has not deployed the market, not that the externalId is unused globally. It says nothing about the shape of a negative result, but an output schema exists to carry that.

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 with zero filler; the core check is front-loaded and the namespace qualifier follows immediately. Nothing could be removed without losing information.

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, read-only existence check with an output schema and full annotation coverage, the description supplies purpose, scope, and namespace semantics. The only real gap is the missing call-site guidance (use before deploying), which is minor relative to the tool's simplicity.

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 0%, so the description is the only source of meaning for externalId, and it only restates it as 'the given externalId'. The 'per-agent namespace' clause does add real semantics — the same externalId can exist under another agent — which partially compensates for the undocumented parameter.

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 names a specific verb (check) and a specific resource/condition (whether this agent already deployed a market with the given externalId), which is far more precise than the sibling kellian_get_market or kellian_list_markets. It does not explicitly contrast itself with those siblings, so an agent must infer the distinction from the 'exists' framing.

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?

Usage is only implied: the title calls it an idempotency check, which suggests calling it before a market deploy, but the description never states when to call it, when not to, or which deployment tool it should precede. No prerequisites or follow-up actions are given.

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