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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds genuinely new behavior beyond the schema: a maximum of three stacked addresses and the instruction to carry the fetched result forward for the rest of the conversation. It still says nothing about error handling for malformed addresses.

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, front-loaded with the purpose before the trigger condition, and no filler. The quoted-mantra phrasing ("open sesame") is unusual but it is the literal trigger, so it earns its place.

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 tool with no output schema, the definition covers what to pass, when to invoke, and what to do with the result. The one gap is that the return shape is never characterized, only that it should be "followed".

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% and the address parameter already carries the format and an example, so the schema does the heavy lifting. The description echoes the accepted prefixes and stacking but adds no syntax detail beyond what the schema provides, making the baseline 3 correct.

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 concrete verb and resource ("Fetch any coldHat address") and enumerates the address subtypes it accepts: a person's hat, a Fabric pattern, a prompts.chat prompt, or a stack. It does not, however, contrast itself with the sibling wear_hat or verify_hat, so the agent must infer why stacking goes to this tool rather than wear_hat.

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?

Gives an explicit invocation trigger (user says "open sesame" with a coldhat.f-keys.com address containing fabric/, prompts/ or +) plus a post-call instruction to follow the result for the rest of the conversation. It stops short of naming the alternatives (wear_hat, verify_hat) or stating when not to use this tool.

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