entity_lookupThe Issafu register entry for a firm, by its register identifier (scheme + value, e.g. lei) or by the slug of its page. Exact match; returns the whole record with its page.
| Name | Required | Description | Default |
|---|---|---|---|
| slug | No | ||
| value | No | ||
| scheme | No | identifier scheme, e.g. lei, fca_frn, tdlr_license |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the behavioral burden. It discloses the matching mode ('Exact match') and the return payload ('returns the whole record with its page'), which is genuinely useful. It says nothing about permissions, authentication, rate limits, or failure behavior when no entity matches, leaving meaningful gaps for a bare lookup tool.
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 resource and the key inputs, then the matching and return semantics. No filler.
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 read-only single-record lookup with no output schema and no annotations, the description covers the inputs, the exact-match behavior, and what is returned (full record plus page). What remains under-specified is error/empty-result behavior and whether slug and scheme/value are alternatives or can combine, but the essentials for correct invocation are present.
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 only 33% (only 'scheme' is documented), so the description must compensate, and it does: it explains that 'scheme' and 'value' form a pair (scheme + value, e.g. lei) and that 'slug' is the page slug. That clarifies the two mutually exclusive lookup paths beyond the raw schema, though it does not spell out the expected identifier formats for other schemes.
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 (retrieve) and resource (Issafu register entry for a firm) and states the two lookup keys (register identifier scheme+value, or page slug). It is clear enough to distinguish a single-record fetch from the many search/list siblings such as entities_search or entities_in, though it never explicitly contrasts itself with them.
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: 'Exact match' signals this is for when you already have a precise identifier or slug rather than a fuzzy query, which helps against entities_search. There is no explicit when-to-use/when-not-to-use statement and no mention of what to do if the identifier is unknown.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.