a2a-mcp-connector

a2a_connect

Validates the Agent Card, connects to the A2A endpoint, and starts streaming turns in a background session. Returns the validator report if unusable; pass a bearer token only if required.

Instructions

Connect to a standard A2A endpoint and start streaming its turns. Validates the Agent Card first and REFUSES to connect if it isn't usable (returns the validator report). On success, starts a background session and returns immediately — then call a2a_wait_turn for the first prompt. bearer is optional (pass it only if the endpoint requires auth). Neither the card URL's contents nor the bearer are echoed back.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "agent_card_url": "<agent_card_url>"
    },
    "name": "a2a_connect"
  }
}

Input Schema

Name	Required	Description	Default
`bearer`	No
`agent_card_url`	Yes

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.2Sep 8, 2026

TDQS

A4.3/5.0

Behavior5/5

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

No annotations are provided, so the description bears full responsibility for transparency. It discloses key behaviors: validation of the Agent Card, refusal with a validator report on failure, starting a background session and returning immediately on success, and the note that neither the card URL nor bearer are echoed back. These details give the agent a solid model of side effects and return behavior.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is moderately concise, containing multiple pieces of necessary information (purpose, validation, success behavior, follow-up, optional parameter, security note). It is well-structured with clear sentences, but slightly longer than strictly necessary. Still, every sentence adds value and there is no redundancy.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's complexity (validation, background session, follow-up action), the description covers the essential context: what to pass, what to expect on failure vs. success, and where to go next (`a2a_wait_turn`). It does not detail the output schema or error conditions, but these are less critical for a first call. Overall, it provides enough context for the agent to use the tool correctly in a typical flow.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description must compensate. It gives clear semantics for `bearer` (optional, only when auth is required), but for `agent_card_url` it only implies from context that it is the endpoint URL. This is partial coverage; a more explicit definition of `agent_card_url` would improve the score.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's primary function: "Connect to a standard A2A endpoint and start streaming its turns." It uses specific verbs (connect, start streaming) and identifies the resource (A2A endpoint). It also distinguishes itself from sibling tools implicitly by describing the connect/start action, which is unique among the listed siblings.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides actionable usage guidance: it tells the user to call `a2a_wait_turn` after success, and explains when to pass `bearer` ("pass it only if the endpoint requires auth"). It does not explicitly contrast with siblings like `a2a_validate` or `a2a_send`, but the sequencing and conditional parameter guidance are clear enough for correct use.

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

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