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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and a closed-world profile, so the safety bar is met structurally. The description adds real value by disclosing the data content a caller receives (address, tax id, terms, hold state) and by clarifying that credit exposure lives elsewhere, which is the main behavioral surprise for this tool. No note on error behavior for a missing/invalid id, which keeps it from a 5.

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 identity of the resource and its contents, followed by the sibling disambiguation. Every clause carries information; nothing is padding.

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?

There is no output schema, but the description compensates by enumerating the returned field groups, which is what an agent needs to decide whether this tool answers its question. The remaining gap is modest: no indication of what a not-found customer yields, but for a read-only single-record fetch the definition is sufficiently complete.

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?

With a single parameter at 100% schema description coverage, the schema already tells the agent everything ("The customer. An existing customer id."). The description adds no syntax, format, or lookup guidance beyond what is already there, so the baseline of 3 applies.

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+resource ("One customer as master data") and immediately enumerates the fields covered (contact facts, billing address, tax id, terms, hold state). It also names the sibling that returns the complementary view (o2c_get_customer for live credit position), so an agent can distinguish the two without opening either schema.

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 parenthetical routes the agent: use this for master data, use o2c_get_customer when the live credit position is needed. That is clear conditional guidance toward an alternative, though it stops short of explicit "when not to use" phrasing or mentioning core_update_customer / core_create_customer as adjacent operations.

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