metadata_set

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

Goes well beyond readOnlyHint=false by declaring the side-effect (attaches XData/extension dictionary metadata to the entity) and the optimistic-locking guard on the predecessor fingerprint. It still does not say what happens on a fingerprint mismatch (error vs. silent no-op) or whether an existing namespace is overwritten, so the mutation semantics remain partially opaque.

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?

Three labeled statements, each carrying distinct information (precondition, side-effect, disambiguation), with the operation and its guard front-loaded. No sentence is redundant.

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 five-required-parameter mutation tool with an output schema and minimal annotations, the description covers the precondition, the write's side-effect and the intended use. Missing are failure behavior on a stale fingerprint and the overwrite/replace semantics of an existing namespace, which an agent would want before calling.

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%, so every parameter is documented in the schema, including the optimistic-locking role of expected_parent_fp. The description only reinforces the fingerprint-match precondition already stated in the schema and adds no format or constraint detail for namespace or value, 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 and resource: set one bounded schema-agnostic JSON metadata namespace on an entity, and labels it as a write operation. It is easily distinguished from metadata_get and metadata_query by the write verb, though it does not name those siblings explicitly.

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 Disambiguation line gives a concrete use case (store engineering properties such as part numbers and materials on entities), and the first sentence gives the calling precondition (document PID and predecessor fingerprint must still match). It never names an alternative tool or a when-not-to-use condition, which keeps it short of a 5.

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