Find the ISIN for a Yahoo Finance ticker symbol, e.g. US0378331005 for AAPL. Returns '-' if unavailable.
Yahoo Finance ticker ISIN. Returns the ISIN for a Yahoo Finance symbol, for example US0378331005 for AAPL. The lookup is experimental, and the isin field is - when none can be found.
| Name | Required | Description | Default |
|---|---|---|---|
| symbol | Yes | Yahoo Finance symbol such as AAPL |
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the burden and handles it reasonably: it discloses that the lookup is experimental and that the `isin` field is `-` when none can be found, which is genuine failure-mode context beyond the schema. It omits auth/rate-limit notes, but for a plain read lookup the caveats given are the important ones.
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 short sentences, front-loaded with the purpose, then the example, then the caveat. Every sentence earns its place with 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 one-parameter tool with no output schema and no annotations, the description covers purpose, input example, and the return value including the `-` fallback, which is exactly what the agent needs since no output schema exists.
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%, so the single `symbol` parameter is already documented. The description's example illustrates the symbol-to-ISIN mapping and output format but adds little about the parameter itself; baseline 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?
Specific verb (returns) and resource (ISIN for a Yahoo Finance symbol), with a concrete example (US0378331005 for AAPL) that makes the intent unmistakable. It is clearly distinct from the many other yahoo_finance_ticker_* tools, though it does not explicitly name any sibling.
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 implied: call it when you have a symbol and need its ISIN. There is no explicit when-to-use/when-not guidance and no named alternative (e.g. yahoo_finance_lookup or yahoo_finance_ticker_info) for broader ticker data.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.